The Kynix Blog

The larger the resistance of the drive, the longer the turn-on time of MOSFET, and the longer the voltage and current overlap time in the switching time, the greater the switching loss. Therefore, the smaller the resistance, the better the drive resistance should be, provided that the drive resistance can provide enough damping to prevent the drive-current oscillation. When designing switch power supply or motor drive circuit with MOSFET, the factors such as on resistance, maximum voltage and maximum current of MOSFET should be considered. In general, the MOSFET tube can be divided into the enhanced and depleted, P-channel or N-channel is a total of 4 types, but the enhanced NMOS tube and PMOS tube are mainly used, in these two commonly mentioned enhanced type, the more commonly used is NMOS, The reason is its small on-resistance and easy to manufacture. However, it is not enough to consider these, because the current will have different losses in various devices, so we must ensure that sufficient current to drive the MOSFET.  Figure 1. MOS schematic diagram In this paper, we will discuss the calculation of the MOS gate drive resistor. The range of the MOSFET drive resistance is between 5~100ohms, so how to further optimize the selection of the resistance value in this range?  Equivalent Drive Circuit Figure 2. Equivalent drive circuit L is the PCB line inductor, according to the professional experience its straight line value is 1nH/ mm, considering other line factors, take L=Length +10 (nH), where Length unit is mm. Rg is the gate drive resistance, and the driving signal is a square wave with a peak value of 12 V. Cgs is the gate and source capacitance of MOSFET, with different tubes and driving voltage its value will be different, here is 1nF. VL+VRg+VCgs=12V Taking drive circuit: Getting differential equation of driving voltage of Cgs: Obtaining Transformation function by method of Laplace transform: This is a third-order system, which is an overdamped vibration when its poles are three different real roots, there are two same solid roots is critical damped vibrations, and there are imaginary roots is underdemped vibrations, which will generate waves of oscillation up and down at the gate of MOFET. This is something we do not want to see, so the choice of gate resistance Rg should make it work in the critical damping and over damping states, but the parameter error is actually working in the overdamped state. Based on the above, therefore, the minimum range of Rg values can be obtained according to the length of the line. Making the length of running line of 20mm and 70mm respectively: L20= 30nH , L70= 80nH, then Rg20=8.94Ω, Rg70=17.89Ω, Here are the voltage and current waveforms   Figure 3. Driving current ripple curve According to the diagram when the Rg is small, the driving voltage surge will be higher, more and more oscillation will exist when the L becomes large, and the performance of MOSFET and other devices will be affected obviously. However, when the resistance value is too large, the driving waveform will rise slowly, while it will have a negative effect when the MOSFET has a large current passing through. In addition, we should note that when L is small, the peak value of driving current is larger, and the output capacity of general IC is limited. When the actual driving current reaches the maximum value of IC output, the output of IC is equivalent to a constant current source. When Cgs is charged linearly, the rising of driving voltage waveform will slow down. The current curve may be shown on the follow (the inductance does not work because the current is constant), this may have an impact on the reliability of the IC, and a small step or burr may occur in the rise of the voltage waveform. Figure 4. Current curve The PWM OUT output of the general IC is shown in the left figure. The internal integration includes the current-limiting resistor Rsource and Rsink, usually Rsource > Rsink, but the actual values are related to the peak driving output ability of the IC. It can be approximately considered that R=Vcc/Ipeak. The drive output capacity of IC is about 0.5A, and meanwhile Rsource is about 20Ω. From the previous voltage and current curves, we can see that the IC driver can drive MOSFET,  but the drive line is usually not a straight line, the inductance may be greater, and in order to prevent external interference, it is necessary to use the Rg drive resistor to suppress. This resistance should be as close as possible to the gate of the MOSFET when considering the effect of the line distribution capacitance. Figure 6. PWM OUT The effect of Rg and L on rising time: (Cgs=1nF, VCgs=0.9*Vdrive) TR(nS)19492302045229Rg(ohm)10221001022100L(nH)303030808080 It can be seen that L has little effect on TR, but Rg has great influence on TR. TR can be estimated approximately by 2*Rg*Cgs. Usually, the rise time is less than 20 percent of the conduction time, and the loss of the MOSFET switch when it is switched on will not cause a heat problem. So when the minimum conduction time of MOSFET is determined, the maximum value of Rg is determined . Generally, the smaller the Rg is, the better, but if considering the EMI, its value should be taken as large as possible. The selection of resistor in MOSFET on-state is discussed above. In order to ensure the fast discharge of gate charge in MOSFET off-state, the resistance should be as small as possible, which is the reason of Rsink<Rsource. To ensure rapid discharge, a diode can be connected in parallel on the Rg. When the discharge resistance is too small, it will also cause resonance due to the inductance of the line (so in some applications there will be a small resistance on the diode.). But the reverse current of the diode is not conductive, at the same time, the Rg is involved in the reverse resonant circuit. Therefore, the peak of reverse resonance can be suppressed. This Diodes usually use a high frequency and small signal tube 1N4148. In practice, we should also consider the influence of the gate and drain of MOSFET and a capacitor Cgd. When MOSFET is on, Rg has to charge Cgd, which will change the voltage rise slope. When off, VCC will charge Cgs through Cgd. In this case, the charge on Cgs must be removed quickly, otherwise, it will lead to abnormal conduction of MOSFET. Figure 7. MOSFET schematic diagram FAQ   1. Why do MOSFETs need resistor? MOSFET gates are exceptionally high impedance. Just like a GPIO pin set to be an input, a pull-down or pull-up resistor helps keep the transistor on or off during power-on. ... When used with a switch or cable that could be disconnected, it is obvious to use a pull-down or pull-up resistor.   2. Do MOSFETs need pull down resistors? You either need a resistor to pull it down to ground or you need the input signal to drive it low. ... You only have to drain the inherent capacitance on the MOSFET gate when you're pulling it low so even at a high resistance to ground the RC time constant is usually relatively short.   3. Does Mosfet have resistance? The MOSFET behaves like a resistor when switched ON (i.e. when Vgs is large enough; check the data sheet). Look in the data sheet for the value of this resistor. It's called Rds(on). It may be a very small resistance, much less than an Ohm.   4. What is the purpose of gate resistor? A gate resistor is used is to slow down the turn-on and turn-off of the MOSFET. (This is more relevant to power circuits that switch a fair amount of current.)   5. What is Mosfet used for? The MOSFET (Metal Oxide Semiconductor Field Effect Transistor) transistor is a semiconductor device which is widely used for switching and amplifying electronic signals in the electronic devices. The MOSFET is a three terminal device such as source, gate, and drain.   6. What is Mosfet and how it works? In general, the MOSFET works as a switch, the MOSFET controls the voltage and current flow between the source and drain. The working of the MOSFET depends on the MOS capacitor, which is the semiconductor surface below the oxide layers between the source and drain terminal.   7. How Mosfet can be used as a resistor? When you slowly increase the gate voltage the MOSFET slowly starts conducting by entering the linear region where it starts developing voltage across it which we call as VDS . In this region, the MOSFET acts as a resistance of finite value.   8. Can Mosfet switch AC? Yes, but you need to connect two back to back to deal with the body diode. Connect the source terminals and gate terminals and connect a floating voltage supply between sources and gates. This circuit is typically called a solid state relay.   9. How much current can a Mosfet handle? Modern MOSFETs can have on resistances of less than 10 milliohms. A little math shows that this device can handle 10 amps with one watt converted into waste heat (power = current2 x resistance). Since many MOSFETs come in TO-220 packages, no heatsink is needed in this instance.   10. How many types of Mosfet are there? four types. There are two classes of MOSFETs. There is depletion mode and there is enhancement mode. Each class is available as n- or a p-channel, giving a total of four types of MOSFETs. Depletion mode comes in an N or a P and an enhancement mode comes in an N or a P.

ⅠIntroductionAs electronic technology advances, there is a greater need for high-speed PCB design. Because they can work at high speeds with integrated circuits for most electronic devices, even simple ones. Some factors and parameters have to be considered when designing a high-speed PCB. Furthermore, you will discover that the fundamental PCB design rules and methods you have mastered are exactly what you need to learn. Needless to say, it will be extremely useful to PCB designers working on high-speed PCB designs.CatalogⅠIntroductionⅡ What is High-speed PCB Design?Ⅲ High-speed PCB Related VideoⅣ When Is a Printed Circuit Board Design Considered High Speed?Ⅴ High-speed PCB Design SkillsⅥ High speed PCB  Design ConsiderationsⅦ Setup for High-Speed DesignⅧ Floorplanning a High Speed PCBⅨ How to Tell If Your Project is High SpeedⅩFAQ Ⅱ What is High-speed PCB Design?High-speed PCB design is any design in which the physical characteristics of your PCB.  such as layout, packaging, interconnection, layer stack up, and so on, begin to impact the integrity of your signals. Furthermore, when you begin designing the boards and encounter issues such as delays, crosstalk, reflections, or emissions, you will enter the world of high-speed PCB design, Because of the attention paid to these issues, high-speed design is truly unique. You may be accustomed to designing a simple PCB  where you focus primarily on component placement and routing. However, it is more important to consider some factors when using a high-speed design, such as how close they are to signals, what width they will be, where you will place the traces, and what types of components they will be connected to. Furthermore, when the factors are considered, it will achieve a high level for your PCB design process.Figure1:What is High-speed PCB Design? Ⅲ High-speed PCB Related Video High-Speed PCB Design Tips - Phil's Lab #25 High-speed PCB Video Description: Quick overview of some general high-speed PCB design tips. Everything from stack-ups, controlled impedance traces, vias, and much more! Ⅳ When Is a Printed Circuit Board Design Considered High Speed?Certain characteristics can help you identify a high-speed  PCB design,  As a result, the design is fast if:It uses  HDMI , Ethernet,  SATA , PCI Express, USB, Thunderbolt, or other high-speed interfaces for fast data transfer; the circuit consists of several sub-circuits connected via high-speed interfaces (LVDS, DSI, CSI, SDIO,  DDR3 , etc.); the time of signal propagation over the track is at least 13 of the time of signal rise; the digital signal frequency is 50MHz or higher;Because the printed circuit board is so small, locating the components becomes a real challenge (especially when you come across a high-speed interface layout  ). Ⅴ High-speed PCB Design SkillsBe familiar with design software that provides advanced options.High-speed designs necessitate a plethora of complex features in your CAD software. Furthermore, there may not be many programs for hobbyists, and it rarely has advanced options based on Web suites. As a result, you must gain a better understanding of a powerful.High-speed routing  When it comes to high-speed traces.  a designer needs to understand the essential routing rules, such as not cutting ground planes and keeping trails short. As a result, keep digital lines a certain distance apart from crosstalk and shield any interference-creating elements from compromising signal integrity.Routing traces  with impedance controlImpedance matching is required for some types of signals with impedances ranging from 40 to 120 ohms. Antennae and a large number of differential pairs are examples of characteristic impedance matched hints.It is critical for designers to understand how to calculate trace width and layer stack for required impedance values. If the impedance values are incorrect, it can have a serious impact on the signal, resulting in data corruption. When creating a PCB  layout or a high-speed PCB  layout.  keep single-ended impedance Zo and differential impedance Zdiff in mind. Figure2: Parameters for Zdiff calculation Length matching traces  High-speed memory buses and interface buses have numerous lines. Because the lines can operate at high frequencies, it is critical that the signals travel from the transmitting terminal to the receiving terminal at the same time. Furthermore, it must have a feature known as length matching. As a result, most common standards define tolerance values that must match length.Figure3: High-speed PCB Design SkillsMinimizing loop areaHigh-frequency signals can cause  EMI  and EMC issues, so high-speed PCB  designers should be aware of these tips. As a result, they must follow basic rules such as having continuous ground planes, reducing loop areas by optimizing current return paths for traces.  and incorporating numerous stitching vias. Ⅵ High speed PCB  Design ConsiderationsThe importance of the PCB  layout cannot be overstated.PCB Design ConsiderationsSchematic considerationsTrace length tuningPCB materials and stack-up demands for high speedHigh-speed placement strategiesDifferential pair and trace length routing Crosstalk, impedance control, and parallelism considerationsUnderstanding stripline and microstripRouting topologies and best routing  practicesSimulators Ⅶ Setup for High-Speed DesignBefore the layout can begin, there are several design and database details that have to be addressed.SchematicWhile there is a lot to set up before you can start the layout of a high-speed design, most people don't give the schematic much thought. Designers need to check the parts, simulate the circuitry, and finish the design. Is the schematic, however, ready to be used for layout? If the designer cannot easily understand the intent of the circuitry, an unorganized schematic can make the PCB  layout difficult. High-speed signal paths, for example, must be laid out sequentially so that the designer can replicate component placement in the layout,  It's also a good idea to highlight parts of the design that you really understand.These include:Critical placement locations, as well as which side of the board certain parts may be required onKeep out zones should be established around critical components.High-speed routing data, such as topologies, measured lengths, and matched lengths.Information about a differential pair and controlled impedance. PCB LibrariesAs with any  PCB  layout.  the component footprints used for high-speed design must be checked and verified, but some additional library work may be required. Some footprints used in high-frequency or RF designs, for example, may require modifications to reduce pad sizes for signal integrity,  In addition, to accommodate high-density design requirements, some footprints may be reduced to their smallest size. However, component footprints should always adhere to industry and manufacturer specifications to the greatest extent possible to meet design for manufacturability (DFM) requirements. Many design tools, including Cadence's Allegro  PCB Editor, include online library browsing capabilities for importing vendor-specific footprint models. Materials and ComponentsBefore you begin the layout.  you must choose the materials that will be used to construct your high-speed circuit board. Harsh operating environments may necessitate a more robust board structure, and the physical properties of the materials will be required for calculated controlled impedance routing  :Consult with your manufacturer to determine whether your board will require high-speed materials.For high-speed and high-frequency applications, enhanced epoxy or PTFE materials may be a better choice.The dielectric constants of  FR-4  may be insufficient to hold the impedance values required, or the design may suffer from greater signal loss than is acceptable.The manufacturer will also need to review and confirm the PCB components. With today's supply chain issues, you'll want to make sure you have enough parts before committing to a design. Board Layer StackupSpecific board layer stack-ups are required for high-speed designs to aid in  EMI shielding and signal integrity,  The primary concern is to include a complete and continuous ground plane on an internal layer. Many boards will also have multiple ground plane layers spread across the board stack up to accommodate multiple layers of transmission line routing in microstrip or stripline configurations. The board layer stack-up must be created in the PCB CAD database or imported from another source. This is where the ability of PCB design systems to communicate directly with the vendor for stack-up information exchange, as demonstrated in the video above, can be extremely useful. Design RulesPCB design systems typically include a comprehensive set of design rules and constraints that can be applied to the design. Component and net classes will already be used in standard circuit board designs to specify spacing rules, trace widths, vias, and other constraints. With a high-speed design, a completely new set of rules should be established, including:Differential pairsSignal pathsRouting topologiesMeasured and matched trace lengthsTrace tuning parameters These rules can be set up for each design, or in many cases, imported from another layout to ease the designer’s workload. System ParametersThe parameters are the last but not least of the setups. Display parameters such as colors and fill patterns, grids, routing preferences, and a slew of others are among them. Designers can improve their tool efficiency by managing these parameters, Let's start laying out the board now that we've completed the high-speed design.Figure5: A PCB CAD system’s parameter setup menu for design colors Ⅷ Floorplanning a High Speed PCBIn a high-speed PCB layout  , there are no specific rules or standards for where components  should be placed. In general, the largest central processor IC  should be placed near the center of the board because it will typically need to interface with all other components  on the board in some way. Smaller integrated circuits (ICs) that connect directly to the central processor can be placed around the central IC  to keep routing between components  short and direct. Peripherals can then be added to the board to provide the necessary functionality.When the main controller IC  is near the center of the board, and other high-speed peripherals are placed around it, the high-speed layout works best. This is one of the reasons why motherboards have a large processor in the center of the board. The Altium Designer MiniPC project has its PCIe, DDR4, USB 3.0, and Ethernet peripherals arranged around the central FPGA SoC to facilitate routing.Figure6: high-speed PCB layoutOnce your components  are in place, you can use your design tools to begin routing your design. This is a critical aspect of high-speed board design because incorrect routing can compromise signal integrity. However, if the preceding steps were followed correctly, signal integrity is much easier to achieve. Set your impedance profile in your PCB design rules so that all routers in the design have the proper width, clearance, and spacing to maintain controlled impedance during routing. Ⅸ How to Tell If Your Project is High SpeedThere are a couple of schools of thought on this. The unfortunate reality is that there is no specific definition of what constitutes a high-speed PCB. It all comes down to a case-by-case assessment. As previously stated, if you're experiencing signal integrity issues on your PCB layout.  it's a good indication that you're working on a high-speed project.There's also the device-specific approach to consider. You'll be working on a high-speed project if you're designing a motherboard, cell phone board, or DSL router board. If you need to incorporate specific technologies into your layouts, such as HDMI, PCI Express, USB, or SATA, be aware that you will be dealing with high-speed design constraints.Figure7: Do you believe your design has a lot of traces? Take a look at this high-speed layout The final point to consider is whether you're working on a design with lumped or distributed circuits. What's the distinction? Designs with physical systems that are all small enough that they interact uniformly are referred to as lumped systems and are not fast. However, if your systems all operate independently within the confines of a larger whole, you have a distributed system and some high-speed design issues to deal with.Here is what you should remember:When the trace length becomes a significant fraction of the wavelength of the fastest signal, high-speed design considerations need to be considered.ⅩFAQ1. What is considered high speed design?High speed design specifically refers to systems that use high speed digital signals to pass data between components. The dividing line between a high speed digital design and a simple circuit board with slower digital protocols is blurry.2. What is high speed design Altium?High-Speed Design in Altium Designer. High-speed printed circuit board design is a process of balancing the circuit design requirements, device technologies, and fabrication materials and methodologies, to deliver a PCB that can transfer signals between the components, with integrity.3. What are high speed interfaces?High-Speed Serial Interface (HSSI) is a short-distance (50') communications interface that is used to interconnect routing and switching devices on slower local-area networks (LANs) with the higher-speed lines of a wide area network (WAN).4. What is high frequency PCB?High Frequency PCB is a type of PCB which is widely used in applications involving special signal transmission between objects. It is available in frequency range of 500MHz to 2GHz and is an ideal choice for mobile, microwave, radio frequency and high speed design applications.5. What is high speed signal in PCB?What is a high-speed signal in a PCB? Signals with frequencies ranging from 50 MHz to as high as 3 GHz are considered high-speed signals such as clock signals. Ideally, a clock signal is a square wave, but it is practically impossible to change its 'LOW' level to 'HIGH' level (and vice versa) instantly.

 Overview of flicker noiseFlicker noise in oscillatorsFlicker Noise in SemiconductorFlicker Noise in op AmpHow to eliminate the flicker noise in op AmpThe working mechanism of flicker noiseEquation of flicker noiseThermal Noise vs. Flicker NoisePros of the flicker noiseCons of flicker noiseApplications of flicker noiseFlicker Noise FAQ Overview of flicker noiseElectronic noise known as flicker noise or 1/f noise happens naturally in almost all electronic parts. It can also result from contaminants in conductive channels, creation and recombination noise inside transistors due to base current, and other factors. Pink noise or 1/f noise are common names for this noise. All electrical devices commonly experience this noise, which has a variety of origins but is typically correlated with direct current flow. It is important in a variety of electronic fields and is important for oscillators used as RF sources.Because the power spectral density of this noise increases with frequency, it is sometimes referred to as low-frequency noise. Below a few KHz, this noise is generally visible. The flicker noise bandwidth ranges from 10 MHz to 10 Hz.Figure 1: The relationship between noise voltage and frequency Flicker noise in oscillatorsFlicker noise is inversely proportional to frequency, or 1/f, and in many applications, such as RF oscillators, there are parts where flicker noise, or 1/f noise, dominates, and other regions where white noise from sources like shot noise and thermal noise, or both, dominate. Within the oscillator the flicker noise expresses itself as sidebands that are near to the carrier, the other kinds of noise stretching away from the carrier with a smoother spectrum, however fading the larger the offset from the carrier.As a result, there is a corner frequency, fc, between the regions where the various types of noise predominate. It is typically discovered that the noise outside of the region where flicker noise predominates is phase noise for a system like an oscillator. As the offset from the carrier increases, this decays until flat white noise takes over.MOSFETs have a greater fc (which can reach GHz levels) than JFETs or bipolar transistors, whose fc is typically below 2 kHz. When building RF oscillators, flicker noise, or 1/f noise, is a crucial type of noise. Although it is frequently disregarded, its influence can be reduced by selecting the right gadget.Figure 2: Flicker noise in ocillators Flicker Noise in SemiconductorThe nature of semiconductor noise and how it is specified in semiconductor devices are covered in the section that follows. Since the origin of each semiconductor noise source is a random process, the noise's instantaneous amplitude is unpredictable. The distribution of the amplitude is Gaussian (normal).Figure 3: Flicker Noise in SemiconductorRemember that the RMS value of noise (Vn) equals the standard deviation (σ) of the noise distribution. A random noise source's RMS and peak voltages have the following relationship: VnP-P = 6.6 VnRMS. The crest factor of any signal is the ratio of peak-to-peak to RMS voltage (VnP-P/VnRMS). Because a Gaussian noise source statistically delivers peak-to-peak voltages that are 6.6 times the RMS voltage or higher 0.10% of the time, the crest factor in Equation 1 is 6.6. The likelihood of surpassing 3.3s is 0.001 in this shaded area under the noise voltage density curve in Figure 2. It's crucial to keep in mind that while random signals (like noise) multiply geometrically in a root sum square (RSS) way, associated signals add linearly. Flicker Noise in op AmpSince flicker noise occurs in addition to the thermal noise present in carbon composition resistors, it is frequently referred to as excess noise there. In varied degrees, other resistor types also show flicker noise, with wire coiled having the least. The type of resistor used will not impact the noise in the circuit because flicker noise is proportional to the DC current in the device, thus if the current is kept low enough, thermal noise will predominate. Scaling up resistors to minimize power consumption in an op amp circuit may result in a reduction in 1/f noise at the expense of an increase in thermal noise. Below is the formula to calculate the flicker noise:Figure 4: Flick noise formulaWhere Ke and Ki are proportionality constants (volts or amps) representing En and In at 1 Hz. fMAX and fMIN are the minimum and maximum frequencies in hertz. How to eliminate the flicker noise in op AmpWhat is the best way to deal with this loud, low-frequency noise? With the limited bandwidth, it is almost impossible to try and filter out this noise without changing the important signal. There is yet some hope, though. Although an amplifier's inherent 1/f noise is beyond the control of a system designer, this noise source can be reduced by choosing the right amplifier for the job. The best option is a zero-drift amplifier if 1/f noise is a major problem. Figure 5: zero-drift op amp chartAny amplifier that uses a constantly self-correcting architecture is referred to as "zero-drift" in the industry, regardless of whether it uses an auto-zero topology, a chopper-stabilized topology, or a combination of the two. No matter the specific architecture used, the objective of zero-drift amplifiers is to reduce offset and offset drift. Other dc features, such common-mode and power supply rejection, are also significantly enhanced during the procedure. The fact that the 1/f noise is eliminated during the offset correction procedure is another significant advantage of these self-correcting designs. This noise source occurs at the input and is relatively slow moving, hence it looks to be a component of the amplifiers offset and gets adjusted accordingly.  The working mechanism of flicker noiseBy raising the overall noise level above the thermal noise level, which exists in all resistors, flicker noise is produced. In contrast, wire-wound resistors have the least amount of flicker noise. This noise is merely present in thick-film and carbon-composition resistors, where it is referred to as surplus noise. Charge carriers that are sporadically trapped and released between the interfaces of two materials may be the source of this noise. Because instrumentation amplifiers use semiconductors to record electrical signals, this phenomena is common in those materials.This noise is merely inversely proportional to the frequency. There are various areas in many applications, such as RF oscillators, where noise predominates, and other areas where white noise from sources like shot noise & thermal noise predominates. A correctly constructed system is typically dominated by this low-frequency noise. Equation of flicker noiseSimply put, nearly all electronic components produce flicker noise. In light of this, the noise is discussed in respect to semiconductor devices, notably MOSFET devices. The formula for this noise is S(f) = K/f. Thermal Noise vs. Flicker NoiseThermal NoiseFlicker NoiseIn order to use SAR data both quantitatively and qualitatively, thermal noise must be eliminated by normalizing the backscatter signal throughout the whole SAR image.Several methods, like ac excitation and chopping, can be used to reduce this noise.The lower parasitic resistance components will result in a reduction in the intensity of thermal noise.Wherever the offset voltage of the amplifier is reduced, this noise intensity will be reduced using a chopper or chopper stabilization approach.Anytime current passes through a resistor, thermal noise results.Semiconductors used in instrumentation amplifiers to record various electrical signals typically experience this noise.Johnson noise, Nyquist noise, and Johnson-Nyquist noise are further names for this sound.1/f noise is another name for this noise.Thermal noise is the noise caused by the equilibrium thermal agitation of the electrons in an electrical conductor.Flicker noise is the sound produced by randomly trapped and released charge carriers at the interfaces of two materials. Pros of the flicker noiseAs the noise is low frequency, it will become quieter if the frequency increases.It is an innate noise present in semiconductor devices that is caused by their physics and manufacturing process.The effects are typically seen in electrical components at low frequencies. Cons of flicker noisePerformance can be hampered by this noise in any precision DC signal chain.In all varieties of resistors, the overall noise level can be raised above the thermal noise level.It is frequency dependant. Applications of flicker noiseCertain passive devices and all active electronic components contain this noise.This phenomena typically happens in semiconductors, which are primarily used to store electrical signals in instrumentation amplifiers.The amplifying capabilities of the device are limited by this noise in BJTs.In resistors made of carbon, this noise is present.This noise typically appears in active gadgets because the charge conveys unpredictable behavior. Flicker Noise FAQFlicker noise is measured in what ways?Similar to other types of noise measurement, flicker noise in current or voltage can be measured. The sampling spectrum analyzer instrument extracts a discrete sample from the noise and uses the FFT method to produce the Fourier transform. Low frequencies are beyond the capability of these sensors to accurately measure this noise. Thus, sampling equipment is wideband and has a high noise level. They can reduce the noise by averaging many sample traces. Due to its narrow-band acquisition, conventional-type spectrum analyzer equipment nonetheless have a higher SNR. What should I do to stop the flickering noise?By a chopper stabilization technique that lowers the amplifier's offset voltage, this noise can be effectively eliminated. Flicker Noise: Why Is It Pink?Pink noise, which has a spectral power density reduction of 3 dB per octave, is also known as flicker noise. As a result, the frequency has an inverse relationship with the pink noise band power. Lower power is produced at higher frequencies. Why is flickering called pink noise?One of the most frequently seen signals in biological systems is pink noise. The term originates from the pink appearance of visible light with this power range. White noise, on the other hand, has an equal strength throughout all frequency ranges. How is flicker noise measured?Flicker noise is proportional to the inverse of the frequency, i.e. 1/f and in many applications such as within RF oscillators there are sections in which the flicker noise, 1/f noise dominates and other regions where the white noise from sources such as shot noise and thermal noise dominate.

CatalogⅠ IntroductionⅡ What is a Toggle Switch?Ⅲ Structure of a Toggle Switch3.1 Lever3.2 Spring3.3 O-ring3.4 Plunger3.5 Moving Armature3.6 Case3.7 BaseⅣ Types of Toggle Switches4.1 SPST (Single Pole Single Throw) Toggle Switches4.2 SPDT (Single Pole Double Throw) Toggle Switches4.3 DPST (Double Pole Single Throw) Toggle Switches4.4 DPDT (Double Pole Double Throw) Toggle SwitchesⅤ Toggle Switch Accessories5.1 Switch Guards5.2 Rubber BootⅥ Applications of Toggle SwitchesⅦ How to Wire a Toggle SwitchⅧ How to Install a Toggle Switch8.1 Installing a Switch in Your Device's Panel8.2 Connecting Your Toggle Switch to Your Device's WiringⅨ Precautions for the Use of the Toggle SwitchⅩ Frequently Asked Questions About Toggle Switches Ⅰ IntroductionYou may not understand what toggle switches are or how they function, but I'm sure you've seen them. Even if you've never seen one in person, you've probably seen old war movies. Consider an image of an ancient airplane cockpit or perhaps an old vehicle dashboard. Toggle switches are the small shiny levers that pilots or drivers use to turn on and off.  A toggle switch is an electromechanical device that flips a lever back and forth to turn on and off a circuit or switch between numerous circuits. This article will show the datails of toggle switches to help you learn more about them. Ⅱ What is a Toggle Switch?The toggle switch is a type of electrical switch distinguished by the presence of a handle or lever that allows the flow of electrical power from a power supply to a device of some kind  to be controlled. An electrical toggle switch can be utilized in a variety of applications, both commercial and residential. Switches of this sort are very straightforward to use and can endure for many years before needing to be replaced. A toggle switch has become a catch-all name for almost any sort of electrical control that uses a handle, lever, or other type of rocking mechanism to manage the flow of electrical current. Some switches, particularly industrial toggles, are quite massive and are built with a metal lever with a handle situated in the centre of the lever. These industrial designs frequently require a tremendous deal of effort to move from one position to another for safety concerns, and may be supplied with locks or timed mechanisms as part of the safety precautions. Other types of switches of this type include little devices that can be controlled with a finger. One of the more popular types of toggles found today is in the home. The toggle light switch is a device that controls the passage of power from the home's main wiring to the wiring of an appliance or fixture. This sort of toggle is typically installed in the wall and covered with a basic switch cover that exposes the lever. It is possible to turn on overhead lights or give electricity to outlets wired directly to the switch by sliding the toggle up and down. In some home designs, a toggle switch right inside the front door controls plugs in the adjacent room, allowing you to easily turn on lamps plugged into those outlets and flood the space with light upon entering the space. While push buttons and virtual keypads are becoming more popular in homes and some commercial and corporate settings, toggle switches remain the most popular choice for directing the flow of power from a source to a device. The switch's simplicity ensures that the possibilities of it breaking down or malfunctioning are low, making it an appealing alternative. Even if the switch finally wears out, the procedure of replacing a toggle switch may usually be completed in minutes and with very little effort. Ⅲ Structure of a Toggle SwitchThis is an example of an ultra subminiature toggle switch with ingress protection that meets the IEC 60529 standard's IP64 standards.It is made up of a lever, a spring, O-rings, a plunger, a moving armature, a case, and a base.  3.1 LeverThe user can toggle between ON and OFF by pressing the lever in the working direction. Levers are often composed of plastic, however on larger devices, some are constructed of metal to boost longevity. 3.2 SpringThe spring is contained within the lever. It pushes the lever outwards and is always in touch with the base. 3.3 O-ringThese are circular rubber components that protect the moving parts in the case and lever from foreign items by sealing the connections between the base and the case. 3.4 PlungerThe plunger is a resin component attached to the bottom of the lever that is designed to be in constant contact with the bottom of the base to limit the lever's movement range. 3.5 Moving ArmatureA U-shaped contact is incorporated in the lever. The tip of the U-shape contact travels with the lever, and the terminal is placed between the tips to activate the switch mechanism's ON state. This makes extraneous things difficult to come between the contacts. 3.6 CaseThe case protects the switch's internal components. It also supports the lever through the upper surface hole. 3.7 BaseThe base, together with the casing, are used to safeguard the switch's internal components. The switch terminals extend from the bottom of the base. Ⅳ Types of Toggle SwitchesWhen choosing a toggle switch, like with any other electrical component, it is critical to evaluate the characteristics of your circuit. Toggle switches are available in a number of voltages, amperages, and power ratings, and are made from a variety of materials. Aside from rating, toggle switches are classified mostly depending on their operating designs. They are classified based on the number of unique positions into which the levers can be switched. A 2-position toggle switch is the most basic kind. This is frequently toggled on and off. Toggle switches are also commonly encountered in three-position configurations. This is where the ease of use ends. There are 4-position, 5-position, and 6-position circuits available, and you can order as many as you need. These multiple position toggle switches, on the other hand, are made for specific applications and are more difficult to find. However, the most common way to categorize toggle switches is by the number of poles and throws. The number of independent circuits that the switch may manage at the same time is referred to as its pole. The number of various outputs that each switch may link its input to is referred to as its throw. Toggle switches are categorised as SPST, SPDT, DPST, DPDT, and unique switches that are not classified under the four popular classifications. 4.1 SPST (Single Pole Single Throw) Toggle Switches SPST On-Off SPST toggle switches control a single circuit. It has two operational modes: ON and OFF. By switching between these two locations, the connection between the conductors linked to its two terminals is either closed or opened. 4.2 SPDT (Single Pole Double Throw) Toggle Switches Single pole double throw toggle switches come in two varieties. They are the two-position ON/ON variation and the three-position ON/OFF/ON variant. *SPDT ON/ON SPDT On-On This is a three-terminal switch that regulates only one circuit. The input is connected to the middle terminal, known as the common. The output is represented by the two outer terminals, which are commonly referred to as A and B. The switch lever has two locations, allowing the input to be connected to either terminal A or B. *SPDT ON/OFF/ON SPDT On-Off-On This is another three-terminal switch that regulates a single circuit. The input, like SPDT ON/OFF, is connected to the common. The main difference with this switch is that the lever has three positions. The circuit is switched between terminals A and B by the end positions. The center position, on the other hand, is an off position. This indicates it does not link the input terminal to either of the output terminals. 4.3 DPST (Double Pole Single Throw) Toggle Switches DPST On-Off This is two SPST switches joined together and controlled by the same lever. This switch has four terminals, two inputs and two outputs. They function as ON/OFF switches. DPST switches are commonly used with 220V equipment to open and close both 110V lines simultaneously. 4.4 DPDT (Double Pole Double Throw) Toggle Switches DPDT toggle switches are classified into three categories. There are two ON/ON positions, as well as three ON/OFF/ON and ON/ON/ON positions. *DPDT ON/ON DPDT On-On This is made up of two SPDT ON/OFF switches that are linked together and controlled by a single lever. It is a six-terminal switch with two independent circuits. The input or common terminals are linked to both A and B terminals at the same time. On the lever, there are only two places. *DPDT ON/OFF/ON DPDT On-Off-On This switch has six terminals and controls two distinct circuits. The lever, on the other hand, has three positions. The inputs are connected to both A and B terminals via the two end locations. However, the middle position does not link the input to any of the output terminals, resulting in an open or off circuit. *DPDT ON/ON/ON  This one is a little more difficult. It is also a three-position switch, with the input going to the center terminals. The lever's two end locations link the input to either both A or both B terminals at the same time. The middle position is what distinguishes this switch. When the lever is centered, one of the inputs is linked to its corresponding A terminal and the other to its corresponding B terminal. As it goes to the middle position, the switch only moves one circuit at a time. There are two types that are utilized to distinguish which side switches over first. These switches are most frequently found on electric guitars. Ⅴ Toggle Switch AccessoriesIf further accessories are required for your project, our toggle switches are available. 5.1 Switch Guards Toggle switch guards are primarily used to safeguard the switch and prevent it from being accidentally switched off or on. The toggle is protected from inadvertent movement by the solid shell. 5.2 Rubber Boot To protect against dust and moisture, a toggle switch rubber boot is employed. The boot completely encloses the base, resulting in a dust-tight seal. Ⅵ Applications of Toggle SwitchesTelecommunications and Networking Equipment (Wireless Network Cards, Handheld Devices, Reset Switches)Instrumentation (Shut-Off Switches, Controllers)Industrial Controls (Grips, Joysticks, Power Supplies)Test and Measurement EquipmentElevator ControlsFood Processing EquipmentBoat and Marine Control PanelsMilitary Applications (Communication Switches)Medical Equipment (Wheelchair Motor Switch)Off-Highway and Construction EquipmentSecurity Systems and Metal Detectors Ⅶ How to Wire a Toggle Switch Step 1Using a test light, locate a fused line as close to the intended location for the toggle switch as practicable. Step 2Install the toggle switch. You can utilize a switch panel for this or drill a hole through which the switch will be mounted. Check your switch; this hole should be 1/2 inch in most cases, but some switches require a larger opening. Step 3Connect a wire from the fused source to the toggle switch's center terminal. Insulated solderless connectors should be used to connect to the switch. How to Wire a Toggle Switch Connect another wire from the switch's second terminal to the device being controlled by the switch. There is no need to run a second wire for ground because vehicles and trucks use the body as the ground side of the circuit. Ⅷ How to Install a Toggle Switch8.1 Installing a Switch in Your Device's PanelStep 1: Before you begin, turn off all power to the device. Before beginning work on your equipment, as with practically all sorts of electrical repair, make sure there is no risk of electric shock. Attempting to change a "live" device is a sure way to injure yourself or produce a short circuit that will permanently ruin your device. *The exact method for detaching your device from its power supply varies based on the device. Disconnect the negative terminal of the battery, for example, in a car, whilst other gadgets may require you to unplug or physically disconnect the power source in some other method. Step 2: Remove the device's panel or casing. To install a toggle switch on a device, you must first obtain access to the item's internal wiring, which normally necessitates the removal of the device's outside paneling or enclosure. Instead of removing the paneling from the entire object, try to remove it solely from the section of the gadget where you plan to place the switch. *For example, if you're putting a toggle switch in your car, you should remove a tiny section of the dash paneling where you wish to install the switch rather than the full dash panel. *Screwdrivers, pry bars, "panel poppers," and other specialist tools may be required. Step 3: The diameter of the switch bushing that will protrude through the panel should be measured. To make room for your toggle switch, you'll normally need to cut a hole in the paneling or casing of your item. Measure the dimensions of the switch bushing (the part of the switch where the "lever" is situated) to determine the size of your hole. *A round hole is typically used for simple toggle switches, however depending on the type of switch, other shapes may be required. Step 4: To fit your hole, drill or cut a hole in the panel. Next, drill a hole in your device's paneling to accommodate your switch. This means drilling with a bit slightly larger than the diameter of the switch bushing for the most basic toggle switches with circular bushings. You may need to use a jigsaw, sandpaper, and/or other equipment to create different-shaped holes. *To drill into wood, plastic, or mild steel, use an HSS (high-speed steel) twist drill bit. If you are drilling through wood, you can also use a spade bit. Step 5: Install the switch from the panel's underside. Finally, insert your switch into the hole you have made for it from the underside. With its mount, secure the toggle switch in place. This normally entails placing the mount over the hole, inserting the toggle switch, and securing it with a nut. *In a basic toggle switch configuration, for example, you may need to thread a jam nut onto the switch's bushing to secure it to the panel mount, then tighten the nut with an adjustable wrench. 8.2 Connecting Your Toggle Switch to Your Device's WiringStep 1: Follow the instructions that came with your switch or device. The electrical setups of the devices on which you would want to put a toggle switch will vary substantially. As a result, no single guide is likely to offer a one-size-fits-all solution. The instructions in this section are intended to serve as general guidelines for constructing a simple on-off ((single pole, single throw or SPST) toggle switch. They should never take precedence over any instructions contained with your toggle switch or the device into which it is being installed. *To save time and avoid unintended damage, call a trained electrician when in doubt. Step 2: Remove the power supply line from your gadget. You must connect your toggle switch to the device's power supply in order for it to act as an on/off switch. Use wire cutters to cut the supply wire of your device at a spot that allows you to route either or both ends of the wire to the switch. Using a wire stripper, remove roughly 12 inch (1.3 cm) of insulation from each end of the wire. Step 3: If neither end of the cable reaches the switch, use a pigtail. A pigtail is a short length of wire with both ends stripped (typically approximately 6 inches (15 cm)). As a sort of "extender," it can be linked to cables that aren't quite long enough to reach your toggle switch. Add a pigtail like this: *Find a wire of the same color and gauge as the present wire. *Cut a length of wire long enough to reach from the supply wire's cut end to the toggle switch. *Remove 12 inch (1.3 cm) of insulation from either end of this wire. *Connect one end of the pigtail wire to the supply wire by twisting the wire ends clockwise together. Twist a wire nut of the appropriate size clockwise over the wire joint until it is snug. Step 4: Connect the power supply to the toggle switch. You've built a break in the device's supply line at this point, so you'll need to install your toggle switch in the middle of the break to regulate the flow of energy through the circuit. The method you use is determined by the sort of toggle switch you have. Please see the following: *If your toggle switch includes wire leads, twist the end of each lead to one of the supply wires (or pigtail extensions) and tighten each wire connection with a wire nut. *If your toggle switch has screw terminals, unscrew the terminal screws, loop the supply wire ends, and hook each loop over a terminal screw so that the loops point clockwise around the shaft of each terminal screw. The terminal screws should then be tightened. *If the toggle switch is soldered, wrap the wire ends around the switch terminals. Needle-nose pliers could come in handy. While holding the end of the solder wire in contact with the terminal, heat each terminal with a soldering iron (but not in direct contact with the soldering iron tip). Withdraw the soldering iron tip when the solder begins to melt, allowing the melting solder to flow and cover the wire-terminal connection. Step 5: Check your switch. When your toggle switch is properly wired, carefully reconnect the device's power supply and test the toggle switch's functionality. If everything functions as it should, you can replace the panel or device housing. Congratulations! You have now installed a toggle switch. Ⅸ Precautions for the Use of the Toggle Switch1. If a load is supplied to the toggle switch terminals while soldering, there may be loosening, distortion, and deterioration of electrical properties due to various situations. Please use it with caution. 2. Because the effects of thermal stress alter when utilizing through-hole printed circuit boards and non-recommended circuit boards, please thoroughly confirm the soldering circumstances ahead of time. 3. Welding twice should be done when the first welding part has returned to normal temperature. Continuous heating can deform the perimeter, loosen terminals, cause them to fall off, and degrade electrical properties. 4. It is vital to confirm the actual mass production conditions while setting welding conditions. 5. The product is developed and manufactured with a DC resistance load in mind. Please confirm individually when employing different loads [inductive load, capacitive load]. 6. Please refer to the suggested dimensions indicated in the product drawing for the mounting holes and patterns of the printed circuit board. 7. The switch should be utilized in structures where the switch is operated directly by humans. It should not be used for mechanical detection. 8. When operating the toggle switch, if a load more than the specified amount is applied, the switch may be damaged. Take cautious not to apply more force to the switch than is specified. 9. Please refrain from touching the operational portion from the side. 10. For the flat shaft rod type, press the switch center as hard as possible. Please keep in mind that the pressing location of the shaft will move when the hinge structure is pressed. 11. After installing the switch, please consult a professional when going through the regenerative hardening furnace due to the hardening of other components' adhesive. 12. If corrosive gas is formed from the surrounding materials of the entire machine when using the switch, it may cause problems such as poor contact, so please confirm thoroughly in advance. 13. The carbon contact point has the property that the contact resistance changes as the pressing load changes. Please utilize it after adequate confirmation when employed in a voltage divider circuit, for example. 14. Be aware of the infiltration of alien stuff in models other than the contained type. Ⅹ Frequently Asked Questions About Toggle Switches1. Is a toggle switch an analogue or digital?A toggle switch is an analog device that cannot generate digital signals. When used as an input with a device such as a microcontroller, it can generate digital signals that the microcontroller can interpret as 1's and 0's. 2. Where would you use a toggle switch?Toggle switches are ideal for modifying the state of system functionalities and preferences. To allow users to choose between two opposed states, toggles can substitute two radio buttons or a single checkbox. It can be difficult to decide which user interface element to employ — radio buttons, checkboxes, or toggles — at times. 3. What is toggle switch used for?The toggle switch is a type of electrical switch distinguished by the presence of a handle or lever that allows the flow of electric current/signal from a power supply to a device or within a device to be controlled. It is a hinged switch that may be set to one of two states: ON or OFF. 4. How do you wire a push button toggle switch?Toggle Switch(1)Drill a hole in the desired area for the switch.(2)Push the switch wire into the hole and connect it to the vehicle's power supply wire with a terminal connector.(3)Using the nut that came with the switch, secure the switch to the hole. 5. How do you start a car with a toggle switch?To begin, crank the ignition key to unlock the steering wheel and the transmission gear shift lock. To start the engine, press the ignition switch. If the starter switch is not spring-loaded, it should be turned off as soon as the engine begins, or the starter will remain engaged. 6. How do you wire a SPST to a toggle switch?(1)Begin by crimping the wire terminals on the wire run you'll be using for the circuit.(2)After that, connect the power wire to the switch's center terminal.(3)After that, connect the wires for your accessory to the top terminal on your switch. 7. What does a toggle light switch look like?The typical toggle switch fits into a small rectangular space in wall plates; switches flick up and down to turn on and off lights. Although most of us are familiar with basic toggle switches, there are a few different types of toggle switches available for toggle switch plates and other plate apertures. 8. What is the difference between button and a toggle switch?Designers frequently confuse toggle switches with toggle buttons because they both control states, but there is a significant distinction. Toggle switches represent system states, while toggle buttons represent contextual states. A switch is a "button" that activates the condition. 9. What is a toggle switch in a circuit?Toggle switches are a form of electronic switch, and they are one of the most fundamental and commonly used electrical components. Electronic switches enable binary on-off control for electrical circuits by halting or resuming current flow. Toggle switches are actuators, which turn a machine on or off. 10. Is a toggle a button?A toggle button allows the user to switch between two states of a setting. Android 4.0 (API level 14) features a new type of toggle button called a switch, which has a slider control and can be added with a Switch object. 11. Can you use a toggle switch as a light switch?The typical toggle switch fits into a small rectangular space in wall plates; switches flick up and down to turn on and off lights. Available in 15A and 20A models, as well as single pole, 3-way, and 4-way configurations. Purchase toggle switches or toggle light switch covers. 12. What is momentary toggle switch?The Greengate Lighting Control Panels feature the Momentary Toggle Switch, which is a low voltage contact closure switch. When toggled up or down, the switch sends a "On" signal to the lighting control panel for a brief period of time and has a center "Off" position. 

In ancient Asia and Europe, "cutting the flesh to cure a boil" has a history of nearly 2500 years, but considering the level of medical treatment and anesthesia at that time, this seems to be more of torture. For irreparable damage to skin tissue, skin grafting is almost the only option considering the body's repulsive reaction. Doctors mainly rely on the removal of the patient's own skin or the skin of others for transplantation repair. Not to mention the unbearable pain, it will also leave new wounds on the patient's skin.In addition, the source of skin grafts for patients with large-area skin injuries is also a problem. The skin after transplantation is very fragile, with sequelae such as weakened sense of touch and decreased immunity.With the efforts of scientists from all over the world, the super-simulation electronic skin model is maturing. If it is put into human trials, this will be a good news for patients. This is a video introducing electronic skin Based on the development of electronic skin in recent years and the shortcomings of current wearable devices, this blog will introduce you to the structure of electronic skin and its future applications in the field of mobile health. Catalog  Ⅰ Introduction to electronic skinⅡ Development of electronic skinⅢ Electronic skin system architecture3.1 Flexible substrate3.2 Flexible battery3.3 Wireless communicationsⅣ Electronic Artificial Skin for   ApplicationⅤ ConclusionFAQ   Ⅰ Introduction to electronic skin Electronic skin, a system that allows robots to produce tactile sensations. It is not only simple in structure, but also can be processed into various shapes, and can even be attached to the surface of the device like clothes, allowing the robot to perceive information such as the location, orientation, and hardness of the object.Basic functions of electronic skin:From obtaining physical stimulation to distributed sensor array;Preprocess the sensor signal;The signal is transmitted wirelessly to higher-level systems (such as smart phones)The electronic skin is equipped with highly sensitive conductive nanomaterials, which can accurately cause slight tremors of the electrical changes of the muscle group. At the same time, the electronic skin is extensible (for example, it supports joint movement), and can even form integrated chemical sensors and biosensors.Therefore, electronic skin enables us to perceive different shapes and textures, temperature changes and different contact pressure levels. And, this is an integrated, scalable sensor network that can provide tactile and thermal signals to the brain, allowing us to operate safely and effectively in the surrounding environment. Human skin with distinctive features is a physical barrier to our interaction with the surrounding environment. Inspired by these features of human skin, researchers are working hard to create a flexible, scalable, and highly sensitive electronic device. Therefore, the development of electronic skin has become a research hotspot, especially in the fields of intelligent robots and electronic medicine.Ⅱ Development of electronic skinThe development of electronic skin technology could be divided into two stages:1）From 1970s to 1990s, the concept of e-skin appeared for the first time and got a preliminary development.2）Since 2000s, more researchers have been involved and have made a significant progress in recent years.In 1974, Clippinger demonstrated the feedback of a discrete sensor for a prosthetic hand. In 1985, General Electric first built a robotic arm sensitive skin which enabled to interact with the environment, placed on a flexible, curved sheet using discrete infrared sensors. In the 1990s, more and more teams began to create large-area, ultra-thin, multi-sensor flexible sheets. Jiang et al. first proposed a bent sensor sheet which obtained by etching thin silicon wafers and then integrating them on flexible polyimide film. In 2000, the organic transistor electronic nose was developed. Later, more achievements were made, such as scalable inverters, flexible active matrix technology, high resolution optical sensors, microstructured pressure sensors and so on. In 2003, the research team at the University of Tokyo in Japan made thin films by using low molecular organic compounds and realized the pressure of electronic skin through the pressure sensors on its surface. In 2010, the University of California, Berkeley, developed a technology to attach nanowire transistors to a sticky substrate, the resulting e-skin therefor could apperceive less than 50 grams of fine pressure and has been subjected to bending 2000 times. A woman scientist of Stanford University Bao Zhenan and her team have developed a highly sensitive flexible plastic film material that mimics human skin and senses subtle pressure. At the same time, the team developed the world's newest stretch solar cells, allowing electronic skin to self-generate electricity. In 2011, a researcher named John A.Rogers introduced an electronic patch for monitoring patient vital signs which described as "electronic skin." This device embedded the sensors in a film and placed the film on a flexible polyester substrate, like a kind of tattoo on the body. Physiological indexes of human health In 2014, electronic skin, developed by a researcher from the Chinese Academy of Sciences, was pasted on the human skin by static electricity, enabling real-time monitoring of physiological indexes of human health such as pulse, heartbeat, body temperature, muscle group vibration and so on, to promptly make a respond with feedback on changes of human health data. Ⅲ Electronic skin system architectureCompared with the current intelligent wearable devices, electronic skin has the characteristics of high sensitivity, ultra-thin, bendability and comfort in guardianship and monitoring the important physiological information of human body. E-skin system is a new type of flexible and extensible sensing system. By making sensors and circuits built on flexible substrates, e-skin systems can obtain unique ductility and more sensible to the various physical, chemical and biological signals. In the field of health care, the emergence of electronic skin will change the imprecise measurement of wearable devices, reduce the number of heavy monitoring equipment in the ward, and enable medical staff obtain the patient's physiological parameters in real time.Figure 1. Architecture of electronic skin systemFigure 2. E-skin structureFigure 3. Relationship between modules of e-skin system in medical applicationsThis system provides flexible circuits on flexible substrate, including microprocessors, Bluetooth and a variety of sensors (temperature, humidity and pressure sensors, blood oxygen, skin impedance and ECG sensors, etc.), which are connected to smart phones via Bluetooth. With the help of big data technology and cloud computing analyzes the data,  giving the diagnosis and treatment in time.Figure 4. Application scene of electronic skin system in mobile healthcareFigure 5. Electronic skin attached to temple to track brain wavesJohn Rogers, a professor of materials at the University of Illinois, Urbana-Champaign, has developed an e-skin called Biostamp, which can track brain waves in real time by sticking a flexible small sensor to a user's temple, able to show your deepest thoughts and feelings and translate them into information.Figure 6. Industrial designers of wearable health-monitoring electronicsIn the above structures, different applications have different requirements for sensors, and microcontrollers are becoming more and more lightweight in the field of electronic skin. So the following three parts of flexible substrate, power management and wireless communication technology will be described in detail.3.1 Flexible substrateOne of the most basic properties of electronic skin is that it has bending property, which can better attach to a large area of surface of human body One of the most basic properties of electronic skin is that it has bending property, which can better attach to a large area of human body surface. To achieve this property, the choice of materials is crucial. Advances in technology have enabled e-skin to be manufactured largely through the development of new materials and new processing methods. At present, polydimethylsiloxane (PDMS) and nanomaterials are commonly used as substrate materials:3.1.1 PDMSPDMS film is one of the most popular flexible substrates, including the advantages of good chemical inertia, being stable in a wide range of temperature, high transparency, variable mechanical properties and good adhesion to silicon wafer. At present, many research groups use PDMS as a flexible substrate. Sigurd Wagner and others used PDMS as a flexible substrate and found that wavy wires built into the film greatly enhanced its extensibility, such as obtaining skin tactile sensor arrays by printing silk screen on the PDMS film. The hypersensitive electronic skin equipment was fabricated by combining homogeneous microcosmic PDMS films with carbon nanocrystalline films.3.1.2 Nanophase materialsNanomaterials are a new type of materials developed in recent years. The current technological trends in the field of new materials are as follows:1. Carbon nanotubes: Compared with the zero-dimensional nanostructures such as carbon black, the one-dimensional carbon nanotubes have higher draw ratio and better electrical conductivity, which are used as conductive filler and then filled with the polymer composite can show lower resistivity and higher electrical conductivity.Figure 7. Schematic of carbon nanotube2. Graphene: Graphene is a hexagonal honeycomb structure consisting of a single layer of carbon atoms. It is the thinnest and strongest superconducting material ever known, which has a superior thermal, mechanical and electrical properties to carbon nanotubes, and with the tunneling effect it obtains a tactile sensor with high sensitivity, having a great application prospect in the field of conductive composite materials. Carbon nanotubes and graphene can be used not only as flexible substrates, but also as various good materials for high sensitivity sensors and flexible batteries. There are teams have so far made achievements in these areas and we are believing that nanomaterials will dominate in the near future.Figure 8. Graphene's atoms arranged in honeycomb pattern3.2 Flexible batteryLightness and softness are two of the most basic characteristics of e-skin. Traditional batteries can no longer meet the requirements of e-skin, but the  foldable and bendable flexible cell has become an indispensable part of e-skin equipment.Table 1. Comparison of current flexible batteryResearch instituteCellPerformanceProLogium Corporation, TaiwanUltra-Thin、Flexible FPC Lithium-Ceramic BatteryCuttable like paper, but cause no fire or explosion under bending, hammering, piercing, and 700-1300 ℃ high temperature gun fireImprint Energy, California, USAFlexible ultrathin zinc polymer battery3D printers in general use can be mass-produced at lower costRice University, USASuper-thin, High -performance flexible lithium free BatteryAfter 10,000 times of charge and discharge, or a thousand bends, it still maintains a capacity of 76%New Jersey Institute of TechnologyFlexible carbon nanotube cellIt can be made into various shapes and sizes, even DIY at homeSamsung Corp.Flexible bendable cellOrganic thin-film solar cellsFraunhofer Institute for Applied Polymer Research, GermanyOrganic thin film solar cellOrganic thin-film solar cellsNorthwestern University,USAFlexible stretchable lithium batteryStretchable, bendable, foldable and rechargeable wirelessly In addition to the flexible batteries mentioned above, a wireless charging technology developed in recent years also provides an alternative to the realization of electronic skin, including kinetic energy (motion, vibration, rotation) thermal energy, piezoelectricity and even radio waves (which can be viewed as wireless energy recovery) can be converted into usable electricity to provide a long-time even permanent energy supply. While it is still hard to really apply it to reality at the moment, it will be a new and innovative breakthrough in the future.3.3 Wireless communicationsIn recent years, in order to meet the requirement of intelligent equipment short-range communication, the automation short-range wireless technology emerges as the times require. At present, among all kinds of short-range wireless communication technologies, several mainstream of it such as Wi-Fi, ZigBeec, NFC, BLEID, UWB and so on become the main means for intelligent devices to communicate with each other at present. In e-skin system, wireless communication is still an indispensable part, and even has a higher requirements in communication performance, application environment and low power consumption.Table 2 Comparison of Wireless Communication TechnologyWireless technologyTransmission range / mMaximum transmission rate /MbpsTransmitting power / MWWi-Fi10-3054<50Zigbee10-100250kbps30NFC<20cm424kbps Bluetooth(BLE)10-1001~10RFID(UHF)<30~100kbps UWB3-10480 Wi-Fi is widely used in smart phones, and its fast transmission speed is an obvious advantage. Bluetooth is a wireless technology with low power consumption, ideal transmission distance and low cost. With the popularity of smart phones and the integration of Bluetooth modules, along with its gradually enhanced storage and computing capabilities, continuous real-time monitoring of the human body becomes possible. At the same time, the smart phone is used in the wearable health monitoring system as the information gateway to transmit the received physiological information, therefore the real-time monitoring of patients' health status has realized together with the emergence of big data technologies and cloud Computing. Bluetooth technology is the first choice for human-body monitoring system to transmit physiological signals in electronic skin. Ⅳ Electronic Artificial Skin for Application Figure 9. Electronic skin to monitor heart rateBiological tissue tends to be curved and soft, and most of the current wearable health monitoring devices are hard, rigid and difficult to achieve a large area of surface attachment. From an application point of view, this is not conducive to obtaining physiological signals from the human body. However because the e-skin has a flexible substrate which can be attached to a large area of tissue surface, and its sensors with high sensitivity can obtain the physiological signals of human body more accurately. Due to the unique properties of e-skin and the development of miniaturization technology, e-skin has great application potential in the fields of health monitoring, prosthesis, robot and so on.Figure 10. Intrinsically stretchable transistorIn the field of health care, electronic skin will have more applications, as shown in figure 11: Blood glucose detection;Speech recognition;Infant temperature monitoring;Intelligent Drug Administration, etc.Figure 11. Applications of electronic skin in health careIt is important for diabetics to be able to know their blood sugar changes all the time. Continuous blood glucose monitoring system can measure the patients’ blood glucose concentration with sensors containing specific enzymes.Speech recognition system(ASR) is an e-skin device attached to the throat of human body. It can monitor the weak pressure changes produced by muscle movement and transform them into speech, helping the deaf and mute to realize their dream of "speaking".Infant monitoring system can monitor the temperature, heart rate and other physical status of the baby in real time, and meanwhile feed back to the intelligent terminal in time.The intelligent drug delivery system can inject drugs regularly and quantitatively by placing them into the e-skin and monitoring the recovery of wounds by intelligent terminal control.With the combination of electronic skin and intelligent equipment, it is only necessary to transmit and analyze the signals obtained by e-skin to the intelligent equipment through wireless communication technology, then it has been able to monitor and provide feedback on the health condition of the human body in real time and in long distance. Electronic skin, as a new type of wearable device, will in the future provide real-time detection of blood pressure, blood sugar, heart rate, body temperature and etc. It is the best choice for real-time diagnosis and evaluation of human health. Ⅴ Conclusion The application prospect of e-skin is very extensive, not only in the field of health care, but also in the fields of consumer electronics, military affairs and even the more sci-fi robot "imitation of human skin", which will bring about revolutionary breakthroughs.With the endless emergence of wearable electronic devices, high sensitivity and miniaturization will become the mainstream trend. The emergence of electronic skin will undoubtedly bring about major technological breakthroughs and innovation opportunities for flexible wearable electronic devices.  FAQ 1. What is electronic skin used for?Flexible circuits inspired by human skin offer options for health monitoring, prosthetics and pressure-sensing robots. 2. What are the advantages of an e-skin?It helps the body to adjust after the transplant. It can make robots more sensitive. The use of tiny electronic wires allows the skin to generate impulses, similar to that of the body's own nervous system. It could lead to advancements in medical equipment. 3. What electronic skin is flexible?Electronic skin refers to flexible, stretchable and self-healing electronics that are able to mimic functionalities of human or animal skin. ... Advances in electronic skin research focuses on designing materials that are stretchy, robust, and flexible. 4. What is the main difference between flexible skin like sensors and the human skin?Like human skin, AISkin also is quite durable; however, while human skin can only stretch about 50 percent, the sensor-based skin can stretch up to 400 per cent of its length without breaking, making the material useful in wearable technology applications. 5. Who invented electronic skin?Researchers from the National University of Singapore have developed an 'electronic skin', capable of recreating a sense of touch thanks to more than 100 small sensors. They hope the technology can be applied to prosthetic limbs, allowing users to feel texture, temperature and pain. 6. Where has electronic skin been developed?National University of Singapore. A team from the National University of Singapore created the skin device, which measures 1 square centimeter. The system contains 100 small sensors that attempt to recreate things like texture, temperature and even pain. The researchers call the device Asynchronous Coded Electronic Skin, or ACES. 7. What can the skin sense?Receptors that let the body sense touch are located in the top layers of the skin - the dermis and epidermis. The skin contains different types of receptors. Together, they allow a person to feel sensations like pressure, pain, and temperature. ... They may sense pain, temperature, pressure, friction, or stretch. 8. What is a skin sensor?Electronic skin sensors, also known as the wearable thin film sensors, can be directly placed on the human body to measure body parameters such as body temperature, heartbeat, sweat composition etc. ... Electronic skin sensors have applications in many areas such as healthcare, sports, robotics and prosthetics, etc. 9. How do you replicate human skin?It was found that the most common materials used to simulate skin are liquid suspensions, gelatinous substances, elastomers, epoxy resins, metals and textiles. Nano- and micro-fillers can be incorporated in the skin models to tune their physical properties. 10. How is electronic skin made?Research into conductive electronic skin has taken two routes: conductive self-healing polymers or embedding conductive inorganic materials in non-conductive polymer networks. ... embedded silver nanoparticles (AgNPs) into a polymer matrix, making the e-skin conductive. 

Introduction IGBT and MOSFET are fully controlled devices and are voltage-driven, that is, the device is turned on or off by controlling the gate voltage. In fact, the structure of the IGBT is an NPN-type MOSFET plus a P-junction, that is, an NPNP structure, which is a P-type BJT driven by MOS in principle. So what is the difference between them? What is the specific connection of them? MOSFET BJT or IGBT - Brief Comparison Catalog Introduction Ⅰ MOSFET & IGBT Review Ⅱ Si IGBT vs SiC MOSFET Ⅲ Different Requirements for Si IGBT and SiC MOSFET 3.1 ON & OFF State 3.2 Short-Circuit Protection 3.3 Interference and Delay Ⅳ IGBT Working Principle by Analogy with MOSFET Ⅴ FAQ Ⅰ MOSFET & IGBT Review MOSFET is a metal-oxide-semiconductor field effect transistor, or metal-insulator-semiconductor. The source and drain of it can be swapped, and they are both N-type regions formed in the P-type backgate. In most cases, these two regions are the same, even if the two ends are reversed, it will not affect the performance of the device. Such devices are considered symmetrical. According to the polarity of its "channel" (working carrier), MOSFET can be divided into two types: N-type and P-type, usually also called NMOSFET and PMOSFET, abbreviations including NMOS, PMOS, etc.IGBT (insulated gate bipolar transistor), is a composite fully controlled voltage-driven power semiconductor device composed of BJT (bipolar transistor) and MOS. Have the advantages of high input impedance of MOSFET and the low on-voltage drop of the GTR. When the GTR saturation voltage is reduced, the current carrying density is large, but the driving current is large; the MOSFET driving power is small, the switching speed is fast, but the on-state voltage drop is large, and the current carrying density is small. The IGBT combines the advantages of the above two devices, and the driving power is small and the saturation voltage is reduced. In simple terms, an IGBT is equivalent to a thick base PNP transistor driven by a MOS. Figure 1. N-MOSFET Architecture Ⅱ Si IGBT vs SiC MOSFET Since the differences between IGBT and MOSFET in structure, working principle and application range are quite detailed, it is impossible to express clearly in one sentence. Next, we will compare the differences between silicon (Si) IGBTs and silicon carbide (SiC) MOSFETs in detail.The electrical parameters and characteristics of Si IGBT and SiC MOS drivers are quite different. The requirements for driving of SiC MOS are also different from those of traditional silicon devices. They have the characteristics of low on-resistance and small switching loss, which can reduce device loss and improve system efficiency, and more suitable for high frequency circuits. It is widely used in new energy vehicle motor controller, vehicle power supply, solar inverter, charging pile, UPS, PFC power supply and other fields.The difference between the two is mainly reflected in the GS turn-on voltage, GS turn-off voltage, short-circuit protection, signal delay and anti-interference, as follows: Characteristic Si IGBT SiC MOSFET Drive Requirements Switching Frequency Low, >30kHz High, 50~500kHz 1) Use high power gate resistors. 2) Optimize the cooling environment. 3) Improve the efficiency of the DC-DC conversion circuit and reduce the overall loss of driving power. Threshold Voltage 5V-6V 1.6V-4.5V Negative pressure shutdown/Miller clamp to prevent false turn-on Switching Time 300ns 50ns 1) Use digital isolation driver chip, the signal transmission delay can reach 50ns, and it has relatively high consistency, and the transmission jitter is less than 5ns. 2) the low transmission delay push-pull chip is selected. Switching-On Time 15V 15V~22V 1) Priority is given to stabilizing the negative voltage to ensure that the shutdown voltage is stable. 2) A negative voltage clamping circuit is added to ensure that it does not exceed the standard during shutdown. Switching-Off voltage -15V~-5V -5V~0V Short-Circuit Withstand Time <10μs 2~5μs A diode or a resistor string is used to detect short circuits, and the shortest short-circuit protection time is limited to about 1.5μs. CMTI 15kV/μs 100kV/μs 1) The common mode anti-interference ability reaches 100kV/μs to transmit the isolation chip for signal transmission. 2) The optimized isolation transformer design is adopted, and its primary side and the secondary side are shielded to reduce mutual crosstalk. 3) The Miller clamp is used to prevent the influence of the switch of the same bridge arm.   Ⅲ Different Requirements for Si IGBT and SiC MOSFET For a fully-controlled switching device, configuring an appropriate on-off voltage is of great significance for the safety and reliability of the device. Due to the difference between IGBT and MOSFET, the requirements for the two are also different.IGBT is a field-controlled device whose turn-on and turn-off are determined by the voltage between the gate(G) and the emitter(E). The working principle of MOS tube (enhancement mode NMOSFET) is to use VGS to control the amount of "induced charges" to change the condition of the conductive channel, and then to control the drain current. 3.1 ON & OFF State 1) Silicon IGBT: Silicon IGBTs of various manufacturers have the same turn-on and turn-off voltage requirements.· The typical turn-on voltage is required to be 15V.· The shutdown voltage value range is -5V~-15V, and customers can choose the appropriate value according to their needs. The common values are -8V, -10V, -15V.· Prioritize stable positive voltage to ensure stable turn-on.2) Silicon carbide MOSFET: Different manufacturers have different switching voltage requirements:· The turn-on voltage is required to be higher than 22V~15V.· The shutdown voltage is required to be higher -5V~-3V.· Prioritize negative voltage stabilization to ensure stable turn-off voltage.· Increase the negative voltage clamping circuit to ensure that it does not exceed the standard when it is turned off. 3.2 Short-Circuit Protection The switching device has the risk of short circuit during operation, and configuring a suitable short circuit protection circuit can effectively reduce the damage caused by the short circuit during the use of the switching device. Compared to Si IGBTs, SiC MOSFETs have shorter short-circuit withstand times.1) Silicon IGBTThe time of surrender and short-circuit of Si IGBT is generally less than 10μs. When designing the short-circuit protection circuit of it, set the detection delay and corresponding time of short-circuit protection to 5-8μs.2) SiC MOSFETGenerally, the short-circuit withstand capability of SiC MOSFET modules is less than 5μs, and short-circuit protection is required to work within 3μs. A diode or a resistor string is used to detect short circuits, and the protection time is limited to about 1.5μs. 3.3 Interference and Delay 1) The impact of high dv/dt and di/dt on the system.When the switching action is performed under the condition of high voltage and high current, the switching of the silicon carbide MOSFET device will generate high dv/dt and di/dt, which will affect the driver circuit. It is very important to improve the anti-interference ability of the driver circuit for the reliable operation of the system. the following way to achieve.· Add common mode choke coil and filter inductor to the input power supply, which reduce the interference of driver EMI to low voltage power supply.· A low-pass filter is added to the rectification part of the secondary side power supply, which reduce the interference of the driver to the high-voltage side.· Use an isolation chip with a common mode immunity of 100kV/μs for signal transmission.· Optimize the isolation transformer design, and use shielding layer on primary side and secondary side to reduce crosstalk between each other.· Use Miller clamp to prevent the influence of the switch of the same bridge arm. 2) Low transmission delayUsually, the application switching frequency of silicon IGBT is less than 40kHZ, and the recommended application switching frequency of SiC MOSFET is greater than 100kHz. The increase of application frequency makes MOS require the driver to provide lower signal delay time. The transmission delay of the SiC MOSFET drive signal should be less than 200ns, and the transmission delay jitter should be less than 20ns, which can be achieved by the following methods.· Using digital isolation driver chip, the signal transmission delay can reach 50ns, and it has relatively high consistency, and the transmission jitter is less than 5ns.· Select push-pull chips with low transmission delay and short rise & fall time. Due to the conductance modulation effect, the on-state specific resistance of high voltage SiC IGBTs is much lower than that of power SiC MOSs, and does not change much as the blocking voltage rating increases. When the conductance modulation effect is fully exerted, the on-state voltage drop of the IGBT drift region is only related to the bipolar diffusion coefficient and bipolar lifetime of the carriers, and will not change with the increase of the on-current. When the operating temperature changes, the on-state voltage drop of the SiC high voltage IGBT decreases with the increase of the junction temperature. This is mainly because the bipolar lifetime of the extra carriers in the SiC epitaxial layer will increase with the increase of temperature. Although the diffusion coefficient will shrink to some extent with the increase of temperature, the greater prolongation of lifetime will eventually make the the bipolar diffusion length increased, thereby reducing the on-state voltage drop. It is especially true in n-channel devices.This is in sharp contrast to the larger increase in the forward voltage drop of the power MOS at high temperature. Silicon carbide p-channel IGBTs have higher on-state voltage drop than n-channel IGBTs at the same current density due to their larger channel resistance, but their volt-ampere characteristics do not change much with temperature. As for the applications, this is undoubtedly an advantage. Figure 2. Comparison of characteristics between SiC IGBT and power MOS under the Same Condition of Withstand Voltage of 20kV. It is not difficult to calculate from the intersection of the equal power consumption curve in the figure and the on-state characteristic curves of these devices: corresponding to the same power consumption of 300W/cm2, the ratio of the on-state current of the silicon carbide IGBT to the silicon carbide power MOS versus p-channel devices and n-channel devices are different, they are 1.5 and 1.8 at room temperature, respectively, and increase to 2.7 and 3.5 at 225°C, indicating that high-voltage and high-current SiC IGBTs are more suitable for high-temperature applications.In a word, compared with Si IGBT, SiC MOSFET not only improves system efficiency, power density and operating temperature, but also puts forward higher requirements for the driver. In order to make silicon carbide MOSFET better in the system, it is necessary to give SiC MOSFET a appropriate driver.   Ⅳ IGBT Working Principle by Analogy with MOSFET IGBT is a Darlington pair composed of GTR and MOSFET: part of which is MOSFET driver, and the other part is thick-base PNP transistor. Figure 3. IGBT Architecture Its simplified equivalent circuit is shown in the figure below, and RN in the figure is the modulation resistance in the base area of the PNP transistor. It can be clearly seen from this circuit that the IGBT is a composite device of Darlington configuration composed of transistors and MOSFET, where the transistor in the figure is a PNP transistor, and the MOSFET is an N-channel field effect transistor, so the IGBT of this structure is called an N-channel IGBT, and its symbol is N-IGBT. Similarly there are P-channel IGBTs, namely P-IGBTs. Figure 4. Simplified Equivalent Circuit The electrical graphic symbols of the IGBT are shown in the figure. IGBT is a field-controlled device, and its turn-on and turn-off are determined by the voltage UGE between the gate and the emitter. When the gate-emitter voltage UCE is positive and greater than the turn-on voltage UCE (th), a channel is formed in the MOSFET and is a PNP. The N-type transistor provides the base current to turn on the IGBT. At this time, the holes (minority carriers) injected into the N- region from the P+ region modulate the conductance of the N- region, reduce the resistance RN of the N- region, and make the IGBT also has a small on-state voltage drop. When no signal or reverse voltage is applied between the gate and emitter, the channel in the MOSFET disappears, the base current of the PNP transistor is cut off, and the IGBT is turned off. It can be seen that the driving principle of IGBT is basically the same as that of MOSFET.① When UCE is negative: J3 junction is in reverse bias state, and the device is in reverse blocking state.② When UCE is positive: UC< UTH, the channel cannot be formed, and the device is in a forward blocking state; UG> UTH, an N-channel is formed under the insulating gate, and conductance is generated in the N- region due to the interaction of carriers modulation so that the device is conducting forward. Figure 5. Hybrid Switch Using Si IGBT and SiC MOSFET 1) ONThe structure of IGBT silicon is very similar to that of power MOSFET, and the main difference is that JGBT adds a P+ substrate and an N+ buffer layer, in terms of it, one MOS drives two bipolar devices (devices with two polarities). The application of the substrate creates a J junction between the P, and N+ regions of the tube. When the positive gate bias causes the inversion of the P base region under the gate, an N-channel is formed, and an electron flow occurs at the same time, and a current is generated exactly in the manner of a power MOSFET. If the voltage produced by this electron flow is in the range of 0.7V, J1 will be forward biased, some holes will be injected into the N- region, and the resistivity between N- and N+ will be adjusted, which reduces the power conduction the total loss of the pass and initiates a second charge flow. The end result is the temporary emergence of two different current topologies within the semiconductor layer: an electron flow (MOSFET current), and a hole current (bipolar). When UCE is greater than the turn-on voltage UCE(th), a channel is formed in the MOSFET to provide base current for the transistor, and the IGBT is turned on. 2) On-State Voltage DropThe conductance modulation effect reduces the resistance RN and reduces the on-state voltage drop. The so-called on-state voltage drop refers to the tube voltage drop UDS when the IGBT enters the on-state, and this voltage decreases with the rise of UCS. 3) Shut DownWhen a negative bias is applied to the gate or the gate voltage is lower than the threshold value, the channel is disabled and no holes are injected into the N-region. In any case, if the current of the MOSFET decreases rapidly during the switching phase, the collector current decreases gradually. This is because there are still minority carriers in the N layer after the commutation starts. This reduction in residual current value (wake) is entirely dependent on the charge density at turn-off, which in turn is related to several factors, such as the number and topology of dopants, layer thickness and temperature. The decay of minority carriers makes the collector current have a wake waveform. Collector current will cause increased power dissipation and cross-conduction problems, especially on devices that use freewheeling diodes.Considering that the wake is related to the recombination of minority carriers, the current value of the wake should be closely related to the Tc, IC of the chip, and has a close relationship with the mobility of holes. Therefore, depending on the temperature reached, it is feasible to reduce the undesirable effects of this current on the end equipment design. When a back pressure or no signal is applied between the gate and the emitter, the channel in the MOS disappears, the base current of the transistor is cut off, and the IGBT is turned off. 4) Reverse BlockingWhen a reverse voltage is applied to the collector, the junction is reverse biased and the depletion layer expands to the N-region. Because the thickness of this layer is reduced too much, an effective blocking ability will not be obtained, so this mechanism is very important. In addition, if the size of this region is increased too much, the voltage drop will continuously increase. 5) Forward BlockingWhen the gate and emitter are shorted and a positive voltage is applied at the collector terminal, the junction is controlled by the reverse voltage. At this time, the depletion layer of the N drift region is still subjected to the externally applied voltage. 6) LatchICBT has a parasitic PNPN thyristor between the collector and the emitter. Under special conditions, this parasitic device will turn on. This phenomenon increases the amount of current between the collector and the emitter, reduces the controllability of the equivalent MOSFET, and often causes device breakdown problems. The thyristor turn-on phenomenon is known as IGBT latch-up. Specifically, the causes of such defects vary, but are closely related to the state of the devices.   Ⅴ FAQ 1. Are there SiC IGBT?Along with the increasing maturity for the material and process of the wide bandgap semiconductor silicon carbide (SiC), the insulated gate bipolar transistor (IGBT) representing the top level of power devices could be fabricated by SiC successfully. 2. Where are SiC MOSFETs used?The primary automotive applications for SiC power MOSFETs, diodes, and modules are onboard electric vehicle (EV) chargers, DC/DC converters, and drivetrain inverters. Plug-in hybrid EVs and battery EVs (BEVs) use onboard chargers to “refuel” the vehicle battery either at home or at a public charging station. 3. What is SiC MOSFET?Silicon Carbide (SiC) MOSFETs exhibit higher blocking voltage, lower on state resistance and higher thermal conductivity than their silicon counterparts. SiC MOSFETs are designed and essentially processed the same way as silicon MOSFETs. 4. Can MOSFET replace IGBT?Due to the higher usable current density of IGBTs, it can usually handle two to three times more current than a typical MOSFET it replaces. This means that a single IGBT device can replace multiple MOSFETs in parallel operation or any of the super-large single power MOSFETs that are available today. 5. What are the advantages of silicon carbide?Silicon carbide MOSFETs have a critical breakdown strength that is 10x of silicon, and silicon carbide MOSFETs can operate at much higher temperatures, provide higher current density, experience reduced switching losses, and support higher switching frequencies. 6. What are the advantages of silicon carbide (SiC) over silicon (Si)?The advantage of SiC starts in the material itself having a 10x higher dielectric breakdown field strength, 2x higher electron saturation velocity, 3x higher energy bad gap and 3x higher thermal conductivity than Silicon. 7. What is the difference between silicon and silicon carbide?Silicon has a breakdown voltage of around 600V, while silicon carbide can withstand voltages 5-10 times higher. ... Silicon carbide can switch at nearly ten times the rate of silicon, which results in smaller control circuitry. 8. What is SiC in semiconductor?SiC (silicon carbide) is a compound semiconductor composed of silicon and carbide. SiC provides a number of advantages over silicon, including 10x the breakdown electric field strength, 3x the band gap, and enabling a wider range of p- and n-type control required for device construction. 9. Which is better MOSFET or IGBT?When compared to the IGBT, a power MOSFET has the advantages of higher commutation speed and greater efficiency during operation at low voltages. What's more, it can sustain a high blocking voltage and maintain a high current. ... The IGBT is also a three terminal (gate, collector, and emitter) full-controlled switch. 10. Why use an IGBT instead of a MOSFET?The main advantages of IGBT over a Power MOSFET and a BJT are: 1. It has a very low on-state voltage drop due to conductivity modulation and has superior on-state current density. ... It canbe easily controlled as compared to current controlled devices (thyristor, BJT) in high voltage and high current applications. 11. Why is MOSFET preferred?Mosfet provides a very good isolation between the gate and the other two terminals compared to bjt. Mosfet can handle more power compared to BJT. The mosfet has a very low power loss and a high speed. Voltage signals can easily operate a mosfet, so it is used in many digital circuits. 12. Where are MOSFETs used?Power MOSFETs are commonly used in automotive electronics, particularly as switching devices in electronic control units, and as power converters in modern electric vehicles. The insulated-gate bipolar transistor (IGBT), a hybrid MOS-bipolar transistor, is also used for a wide variety of applications. 13. Why IGBT is very popular nowadays?With its lower on-state resistance and conduction losses as well as its ability to switch high voltages at high frequencies without damage makes the Insulated Gate Bipolar Transistor ideal for driving inductive loads such as coil windings, electromagnets and DC motors. 14. How many terminals are in a MOSFET?four terminalsThe MOSFET has four terminals: drain, source, gate, and body or substrate. 15. Why is IGBT bipolar?IGBTs is a bipolar device that utilizes two types of carriers, electrons and holes, resulting from the complex configuration that features a MOSFET structure at the input block and bipolar output, making it a transistor that can achieve low saturation voltage (similar to low ON resistance MOSFETs) with relatively fast. 16. How many types of IGBT are there?two typesInsulated Gate Bipolar Junction Transistor (IGBTs) are normally classified into two types. (ii) Punch Through [PT-IGBT]. These IGBTs are also referred to as symmetrical and asymmetrical IGBTs. These varieties of IGBT differ widely with regard to their fabrication technology, structural details etc. 17. What is full MOSFET?MOSFET stands for metal-oxide-semiconductor field-effect transistor. It is a field-effect transistor with a MOS structure. Typically, the MOSFET is a three-terminal device with gate (G), drain (D) and source (S) terminals. 18. How does an IGBT work as a switch?As defined by being a transistor, an IGBT is a semiconductor with three terminals which work as a switch for moving electrical current. Just as the word “gate” suggests, when voltage is applied to the gate, it opens or “turns on” and creates a path for current to flow between the layers. 19. Can I use transistor instead of MOSFET?It very much depends on the application. BJTs can be cheaper than FETs. This is especially true for high voltage switching where the much larger die area of FETs make them much more expensive. 20. Can IGBT conduct in reverse direction?No. The IGBT cannot conduct current in the reverse direction (from emitter to collector) even with a positive Vge applied to it, because it has a bipolar-type structure. ... However, the gate has no control over this reverse current flow; it is simply the forward biasing of the diode that allows it.