voltage Related Articles

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.

ⅠIntroduction Motor capacitors temporarily store an electrical charge to provide additional torque and improve the performance and efficiency of a motor. Start capacitors provide added torque during motor startup and then exit the circuit when the motor reaches operating speed. Run capacitors assist the motor in maintaining a consistent charge while it is running. By balancing working power and supplied power, power factor correction capacitors reduce motor power consumption caused by heavy inductive loads. Motor capacitors are most frequently used to power motors in HVAC applications such as fans, blowers, and compressors, but they are also found in pumps, conveyors, and machine tools. What does a run capacitor look like? Catalog ⅠIntroduction Ⅱ Two Types of Motor Capacitor 2.1 What is the run capacitor？ 2.2 What is the starter capacitor? Ⅲ Run Capacitor Related Video Ⅳ Specifications of Run Capacitor Ⅴ Faulty Run Capacitor 5.1 When Is It Time to Replace a Run Capacitor? 5.2 Causes of Failure Ⅵ How To Replace a Start Run Capacitor? Ⅶ How Do They Work In an HVAC System? Ⅷ Dual Capacitors vs. Run Capacitors vs. Run Capacitors   Ⅱ Two Types of Motor Capacitor Motor capacitor include two types: run capacitor and starter capacitor. Let us have a look at the two capacitors.   2.1 What is the run capacitor？ Run capacitors are rated in the 3–70 microfarad range (uF). Voltage classification is also applied to rate run capacitors. The voltage levels are 370V and 440V. Starting capacitors have ratings greater than 70 microfarads (uF). Run capacitors are designed for continuous duty and remain energized throughout the lasting of the motor's operation. A capacitor is required to power a second phase winding in a single-phase electric motor. This is why the sizing is so crucial. The motor will not have an even magnetic field if the incorrect run capacitor is installed.This case will lead to the rotor hesitating at uneven spots. This pause causes the motor to become noisy, increases energy consumption, reduces performance, and causes the motor to overheat.   2.2 What is the starter capacitor? In contrast to run capacitors, which have a specific uF rating, starting capacitors are housed in a black plastic case and have an uF range. Start capacitors (with ratings of 70 microfarads or higher) are classified into three voltage classes: 125V, 250V, and 330V. A 35 uF at 370V run capacitor and an 88–108 uF at 250V start capacitor are two examples. Start capacitors increase motor starting torque and allow a motor to be rapidly cycled on and off. Start capacitors are designed for one-time use only. Start capacitors are energized for a short time, allowing the motor to reach 3/4 of its full speed before being disconnected from the circuit.   Ⅲ Run Capacitor Related Video   Start Capacitors & Run Capacitors for Electric Motors - Differences Explained by TEMCo run capacitor video descriped:  What's the difference between a start capacitor and a run capacitor? Can you use them interchangeably? See why these two types of capacitors cannot always be substituted for one another.   Ⅳ Specifications of Run Capacitor Most run capacitor applications employ capacitance ratings of 2.5-100 uf (microfarads) and voltages of 370 or 440 VAC. They are also usually rated at 50 and 60 Hz. Cases are typically round or oval in shape, with a steel or aluminum shell and cap. Terminals are typically 14" push-on terminals with 2-4 terminals per connection post.   Specifications of Run Capacitor   Ⅴ Faulty Run Capacitor 5.1 When Is It Time to Replace a Run Capacitor? As a general rule, a run capacitor will greatly exceed the start capacitor of the same motor. A run motor capacitor will wear down at different levels, making it more complicated to determine if it needs to be replaced. When a run capacitor begins to perform outside of its allowable range, the rated capacitance value usually drops. A "tolerance" will be specified for most standard motor run capacitors, describing how close the actual value may be to the rated capacitance value. It is usually within +/- 5% to 10%. For most motors, as long as the actual value is within 10% of the rated value, you're good to go. A run capacitor will occasionally bulge from internal pressure due to a flaw in the capacitor's construction or a non-capacitor-related motor issue. Most modern run capacitor designs will open the circuit, disconnecting the internal spiral membrane as a precautionary measure to keep the capacitor from popping. The test is simple: it is time to replace in both cases that it is  bulging and there is  no continuity between the terminals, Run Capacitor   5.2 Causes of Failure Depending on how close the run capacitor is to its design life, there could be several reasons why it failed.   Diagnosing and Replacing a Run Capacitor   Ⅵ How To Replace a Start Run Capacitor? When a new motor is installed, a new fan capacitor should always be installed. It is always a good idea to photograph or write down the wire coloring and connections. Turn off the power to the HVAC unit and use a meter to ensure it is completely off.Locate and remove the side panel where the electricity is fed into the unit.Locate the Stat Run Capacitor;  there will only be one in a Dual Run capacitor. If there are two, only the fan motor capacitor has to be replaced.Check the MFD and voltages, then connect the new connections from the old capacitor to the new capacitor one leg at a time to ensure they are correct. (For example, if you have two capacitors, one is for the compressor and the other is for the fan motor.)   Ⅶ How Do They Work In an HVAC System? A Start or Run Capacitor can be combined into a single capacitor with three leads known as a Dual Capacitor, or it can be split between two separate capacitors. The Start Capacitor gives a fan motor the torque it needs to start spinning and then turns off, whereas the Run Capacitor stays on and provides extra torque to the motor when needed. The motor will most likely not start if the Start Capacitor fails. If a Run capacitor fails, the motor will start, but the running amperage will be higher than usual, causing the motor to run hot and have a short life expectancy. There are three connections on a Dual Capacitor: HERM, FAN, and COM. HERM is for the Hermetically Sealed Compressor, FAN is for the Condenser Fan Motor, and COM is for the Contactor, which powers the Capacitor. If the unit has two capacitors, the larger of the two is the Run Capacitor. Keep in mind that the compressor frequently necessitates the use of a HERM capacitor (compressor). Run Capacitor circuit   Ⅷ Dual Capacitors vs. Run Capacitors vs. Run Capacitors The only benefit we can get from the dual-run capacitor design is that it comes in a small package with only three connections. Aside from that, there is no distinction between run and dual run capacitors. If there is enough space for mounting, it is acceptable to replace your original dual-run capacitor with two separate run capacitors. They typically have "C" connections for "common," "H" or "Herm" connections for "Hermetic Compressor," and "F" connections for "Fan." They'll also have two different capacitor ratings for the two parts. Start capacitors provide a high capacitance value required for motor starting in a very short (seconds) time. They are only designed for intermittent duty and will fail catastrophically if left on for an extended time. Run capacitors are continuous duty because they provide continuous voltage and current control to a motor's windings. They typically have a much lower capacitance value.   Ⅸ FAQ 1. What happens when a run capacitor goes bad? A bad motor capacitor may cause starting problems or could shut off the motor while running. Same principle on the dirty coil. ... If a Run capacitor goes bad then a motor can turn on but the running amperage will be higher than normal causing the motor to run hot and have a short life expectancy. 2. What is the difference between a capacitor and a run capacitor? The start capacitor creates a current to voltage lag in the separate start windings of the motor. The current builds up slowly, and the armature has an opportunity to begin rotating with the field of current. A run capacitor uses the charge in the dielectric to boost the current which provides power to the motor. 3. Can I run my AC without a capacitor? Most of the motors in your air conditioner can't run without a good capacitor. Like I said, they support these motors. They help the motor start and run efficiently. Some people have gone out to their air conditioner and noticed the fan wasn't spinning on their AC as it should be. 4. Can I use a run capacitor in place of a start capacitor? The capacitance and voltage ratings would have to match the original start capacitor specification. A start capacitor can never be used as a run capacitor, because it cannot not handle current continuously. 5. Do I need a start or run capacitor? Run capacitors are designed for continuous duty, and are energized the entire time the motor is running. Single phase electric motors need a capacitor to energize a second phase winding. ... Start capacitors increase motor starting torque and allow a motor to be cycled on and off rapidly. 6. What size run capacitor do I need? The run capacitor should have the exact microfarad (uf) that the motor is rated for. Capacitors rated above 70uf are considered Start Capacitors and are generally removed from the circuit electrically during operation. This is where the rule of +/- 10% of the rating came from, for Start Capacitors ONLY!

ⅠIntroduction Channel MOSFETs are a type of Metal Oxide Semiconductor Device. It consists of the n-substrate in the center with a high concentration of light doping. This is a list of the three-terminal devices. It has unipolar characteristics because the majority of the charge carriers are essential for its operation. Because of the two p materials used in the circuitry, the majority of the carriers are holes. It is further subdivided based on the presence of channels.   Catalog ⅠIntroduction Ⅱ What is P-Channel  MOSFET? Ⅲ P Channel MOSFET Characteristics Ⅳ How P-Channel MOSFETs Are Constructed Internally? Ⅴ Types of P-Channel MOSFET 5.1 P Channel with Enhancement MOSFET 5.1.1  How a P-Channel Enhancement-type MOSFET Works? 5.1.2 How to Turn on a P-Channel Enhancement Type MOSFET? 5.1.3 How to Turn Off a P-Channel Enhancement Type MOSFET? 5.2 P Channel Depletion MOSFET 5.2.1 How a P-Channel Depletion-type MOSFET Works? 5.2.2 How to Turn on a P-Channel Depletion Type MOSFET? 5.2.3 How to Turn Off a P-Channel Depletion Type MOSFET? Ⅵ How to use only positive voltage in this p-channel MOSFET tutorial? 6.1 VGS Threshold 6.2 P-Channel MOSFET Tutorial and Explanation Ⅶ FAQ     Ⅱ What is P-Channel  MOSFET?   A MOSFET is formed when a lightly doped N-type substrate is connected to two highly doped P-type materials. Doping refers to the concentration of impurities added to the atom. The p-channel formed between the two P-type substrates could be the consequence of induced voltages or it could have existed previously.    MOSFET Symbol    Ⅲ P Channel MOSFET Characteristics   The voltage controlled devices are represented by MOSFETs.These devices have high input impedance values.The conductivity of the channel in a P-channel is caused by the application of negative polarity at the gate terminal.     Ⅳ How P-Channel MOSFETs Are Constructed Internally?    P-Channel MOSFET   A P-Channel MOSFET is consists of a P channel, which is a channel that is mostly made up of hole current carriers. N-type material is used for the gate terminals.  How the transistor operates and whether it turns on or off  is determined by the amount and type of voltage (negative or positive)     P-Channel MOSFET as a Switch. Turn ON a 12V Motor with Arduino. (Step-By-Step Guide)     Ⅴ Types of P-Channel MOSFET   The p-channel MOSFET’s are classified as:   (1)P-channel with the Enhancement MOSFET (2) P-channel with the Depletion MOSFET     5.1 P Channel with Enhancement MOSFET   This MOSFET is constructed with a lightly doped n-substrate. The length separates the two heavily doped p-type materials (L). This L is referred to as the channel length.   Above the substrate, a thin layer of type silicon dioxide is deposited. This layer is commonly referred to as the dielectric layer. The source and drain are formed by the two P types. The gate terminal is formed by the aluminum plating used above the dielectric. The ground is connected to the source and the body of the MOSFET.   The gate terminal has been subjected to a negative voltage. Because of the effect of capacitance, the positive concentration of charges settles below at the dielectric layer. Because of repulsive forces, the electrons present at the n substrate are shifted, and the uncovered value of the positive ions layer can be found there. In an n-type substrate, the holes, which are minority carriers, combine with a few electrons to form a bond.   However, further application of the negative voltage cracks the covalent bonds, thereby breaking the pairs formed between electrons and holes. It results in the formation of holes and an increase in the carrier concentration of holes in the channel. When a negative voltage is applied to the drain terminal, the channel becomes conductive, allowing current to flow through the transistor.     5.1.1  How a P-Channel Enhancement-type MOSFET Works? circuit example     5.1.2 How to Turn on a P-Channel Enhancement Type MOSFET?     To turn on a P-Channel Enhancement-type MOSFET, apply a positive voltage VS to the MOSFET's source and a negative voltage to the MOSFET's gate terminal (the gate must be sufficiently more negative than the threshold voltage across the drain-source region) (VGDS). A current will be allowed to flow through the source-drain channel as a result of this.   With a sufficient positive voltage, VS, applied to the source and load, and a sufficient negative voltage applied to the gate, the P-Channel Enhancement-type MOSFET is fully functional and operating in the active 'ON' mode.     5.1.3 How to Turn Off a P-Channel Enhancement Type MOSFET?   There are two ways to turn off a P-channel enhancement type MOSFET. You can either disconnect the bias positive voltage, VS, which powers the source. Alternatively, you can disable the negative voltage applied to the transistor's gate.     5.2 P Channel Depletion MOSFET When compared to n channel depletion MOSFETs, the formation of p channel depletion is simply in reverse. Because of the presence of p-type impurities in the channel, it is pre-built. When a negative voltage is applied to the terminal gate, the free holes that represent the minority carriers at the n-type are attracted to the channel of the positive type impurity ions. When a drain terminal is reverse biased in this condition, the device begins to conduct, but as the negative voltage in the drain terminal increases, the depletion layer forms.   This region is affected by the concentration of the layer formed by positive ions. The width of the depletion region influences the conductivity of the channel. The current at the terminal is controlled by varying the voltage value of the region. Finally, the gate and drain retain their negative polarity, while the source maintains its zero value.     5.2.1 How a P-Channel Depletion-type MOSFET Works?   circuit  P-Channel Depletion-type MOSFET   5.2.2 How to Turn on a P-Channel Depletion Type MOSFET? The gate voltage feeding the gate terminal should be 0V for maximum operation if you switch on a P-Channel Depletion-Type MOSFET. The drain current is at its maximum when the gate voltage is 0V, and the transistor is in the active 'ON' region of conduction.     5.2.3 How to Turn Off a P-Channel Depletion Type MOSFET?   There are two methods for turning off a P-channel MOSFET. You can either switch off the bias positive voltage, VDD, which powers the drain, or you can turn it back on. Alternatively, you can apply a negative voltage to the gate. The current is cut down when a negative voltage is used to the gate. As the gate voltage, VG, becomes more negative, the current decreases until it reaches cutoff, at which point the MOSFET is in the 'OFF' state. It prevents a great source-drain current from flowing.   MOSFET transistors are applied for switching as well as amplifying. MOSFETs are among the most widely used transistors today. Because of their high input impedance, they draw very little input current, which is simple to manufacture, can be made very small, and consume very little power.       Ⅵ How to use only positive voltage in this p-channel MOSFET tutorial?   6.1 VGS Threshold   VGSth: an abbreviation for Voltage Threshold from Gate to Source is one of their critical properties we need to know about using MOSFETs. The resistance between the DRAIN and SOURCE pins changes as the voltage difference between those two pins changes. This is the threshold at which a MOSFET turns on and off.   The resistance changes depending on whether the MOSFET is N-Channel or P-Channel.     6.2 P-Channel MOSFET Tutorial and Explanation   For a P-Channel MOSFET, look at the VGSth. VGSth is a negative value, as you may have noticed. As an example, consider the datasheet for an IRF5305.     specification   The specification of VGSth is -2.0V to -4.0V. So, how could this MOSFET work with an Arduino, LaunchPad, Raspberry Pi, or any other microcontroller? Is it really necessary to generate negative voltages?     It’s about the difference:   This is where the "negative voltage" myth comes into play: Because the datasheet says negative, you need negative voltage to work. Datasheets, on the other hand, never lie (except when they do...).   Let's take a literal look at what the specification says. "A negative four-volt voltage from gate to source." You could read it as "GATE voltage value minus SOURCE voltage value" in other words.   Consider the following voltages in this "high-side switch" configuration:     negative voltage     The GATE now has a voltage of 5 volts. The SOURCE is 5 volts as well. It means that the Vgs is 5V – 5V = 0V. In this case, the Vgs is 0 volts. This voltage indicates that the MOSFET is off, or that it is open.   This is the same circuit as before, but the GATE is now connected to ground rather than 5 volts.       circuit  example in 5 volts     Let's take another look at the SOURCE and GATE. The SOURCE remains at 5 volts. However, the GATE is now at the ground, indicating that it is 0V. If you subtract the GATE voltage from the SOURCE voltage, you get 0V – 5V = -5V. This will activate the MOSFET.   Have you noticed what just happened? Using only positive voltage supplies, we obtained a "negative" voltage...     Why use N-Channel over P-Channel?   A tutorial on when to use an n-channel and p-channel MOSFET would be required. A great application for P-Channel is in a circuit where the voltage levels of your load and logic are the same. For example, suppose you're attempting to activate a 5-volt relay with an Arduino. The current required by the relay coil is too high for an I/O pin, but the coil requires 5V to function. Use a P-Channel MOSFET to turn on the relay from the Arduino's I/O pin in this case.   If your load voltage is higher, such as 12 or 24V, you should consider using an N-Channel MOSFET in a "low side" configuration.   Ⅶ FAQ   1. How do you test P MOSFET? Hold the MosFet by the case or the tab but don't touch the metal parts of the test probes with any of the other MosFet's terminals until needed. 2) First, touch the meter positive lead onto the MosFet's 'Gate'. 3) Now move the positive probe to the 'Drain'. You should get a 'low' reading.   2. When would you use a MOSFET? 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.   3. What is 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.   4. What are the types of MOSFET? Different Types of MOSFET Transistors PMOS Logic. As previously mentioned, the integration of a MOSFET allows for high levels of circuit efficiency when compared with BJTs. ... NMOS Logic. ... CMOS Logic. ... Depletion Mode MOSFET Devices. ... MISFETs. ... Floating-Gate MOSFETs (FGMOS) ... Power MOSFETs. ... DMOS.                  

Introduction Capacitors are now commonly used as decoupling capacitors, DC blocking capacitors, or as matching capacitors due to their characteristics of blocking DC while passing AC. But in practical applications, DC can charge the capacitor and pass through it. Is this contrary to its characteristics? Why can DC charge the capacitor? Here we will discuss this issue in details. Charging and Discharging of Capacitor -RC Circuit Catalog Introduction Ⅰ Capacitor Charging Principle Ⅱ Why Capacitor Charges in DC? Ⅲ Capacitor Transient and Steady-state Processes Ⅳ Capacitor Circuit Analysis and Calculations Ⅴ FAQ Ⅰ Capacitor Charging Principle A capacitor is a component that can store electrical energy. As one of the most commonly used electronic components, the simplest capacitor is composed of plates at both ends and an insulating dielectric (including air) in the middle. After being energized, the plates are charged to form a voltage (potential difference), but due to the insulating material in the middle, the entire capacitor is non-conductive. However, this situation is under the premise that the critical voltage (breakdown voltage) of the capacitor is not exceeded. In fact, any substance is relatively insulating. When the voltage across the substance increases to a certain level, the substance can conduct electricity. We call this voltage breakdown voltage.It is the same for the capacitor. After the capacitor is broken down, it is not an insulator. In an AC circuit, because the direction of the current changes with time as a certain function. The process of charging and discharging a capacitor takes time. At this time, a changing electric field is formed between the plates, and it is also a function of time. So current passes between capacitors in the form of an electric field.Capacitors are similar to batteries in that they also have two electrodes. Inside the capacitor, the two electrodes are connected to two metal plates separated by a dielectric. When the capacitor is connected to the power supply, under the action of the electric field force, the free electrons of the capacitor plate connected to the positive electrode of the power supply will move to the negative electrode. The positive electrode is positively charged due to the loss of negative electrons, and the negative electrode is negatively charged due to its negative electrons. In addition, the charges on the positive and negative plates are equal, with opposite signs.The directional movement of the charge forms a current. Due to the repulsion of the same charges, the current is the largest at first, and then gradually decreases. During the charge movement, the charge stored in the capacitor plate continues to increase, and the charge stops moving when the voltage between the two plates of the capacitor is equal to the power supply voltage. That is, the current I=0, the switch is closed, and the positive and negative plates of the capacitor are neutralized through the connection of the wires. When the switch is closed, the positive charge of the positive pole of the capacitor can be moved to the negative pole and neutralized. When the charge gradually decreases, the current decreases, and the voltage gradually decreases to zero.   Ⅱ Why Capacitor Charges in DC? Why is there a charging current that lasts for a period of time when using DC to charge a capacitor? At this time, the circuit is equivalent to an open circuit, there is no continuous current without a loop, and the capacitor charging has time, not instantaneously, so the instantaneous current is not the answer. Having a potential difference, how does a circuit without a closed loop produce a charging current that lasts for a period of time? Figure 1. Transition Process When Charging the Capacitor The voltage across the capacitor is not allowed to change suddenly. So when the power is turned on, the voltage across the capacitor is equal to zero, and then the voltage rises exponentially until it enters a steady state. The capacitor after entering the steady state is equivalent to an open circuit. In fact, the capacitor can block the constant direct current and disconnect when it fully charged in the circuit. According to the leakage resistance of the capacitor, the charge can be stored in the capacitor for a long period of time.When Usr is instantly added to the resistor-capacitor circuit, because the voltage across the capacitor is not allowed to change suddenly, the capacitor is equivalent to being short-circuited at this time. So at time 0, the current flowing through the capacitor and resistor R is .Then the capacitor began the charging process, and the current became smaller and smaller. After 5 times the RC time, the capacitor charging is basically over and the current is reduced to zero. Since then, it has entered a steady state. The RC(τ) here is called the time constant.We know that resistance is equal to the ratio of voltage to current, that is, R=U/I. We also know that the capacitance C is equal to the ratio of the electric quantity Q to the voltage U, and the electric quantity Q is equal to the product of the current I and the time t .It turns out that the product of resistance and capacitance is time. The unit of resistance is ohms and the unit of capacitance is farads, so the unit of time is seconds.In Figure 1, when the capacitor is charged, the voltage across it is .We find Uc when t=0, 1RC, 2RC, 3RC, 4RC, and 5RC, as follows: It can be seen that when time t=0, the voltage across the capacitor is equal to zero; when t=5RC, the voltage across the capacitor is almost equal to the input voltage.Let's look at the current flowing through the capacitor, its expression is as follows: When t=5RC, where .It can be seen that the current at this time is almost equal to zero. Therefore, the transient process and steady-state process of the capacitor must be clearly distinguished.   Ⅲ Capacitor Transient and Steady-state Processes 1) There are transient and steady-state processes in the capacitor charging circuit.2) At the beginning of capacitor charging, it must be considered that the voltage across the capacitor does not allow sudden changes, which is an important principle.3) The transient process generally ends after 5τ.4) For Figure 1, at the moment of the transient start, the capacitor voltage Uc is equal to zero, and the current Ic is equal to the maximum value. We know from Ohm's law that the equivalent resistance of the capacitor is equal to zero . Usually we say that the capacitance at this time is equal to the short circuit i. In the steady state at the end of the transient, the capacitor voltage Uc is equal to the input voltage Usr, and the capacitor current Ic=0. According to the Ohm's law that the equivalent resistance of the capacitor is equal to infinity . At this time, the capacitance is equivalent to an open circuit.5) If the input signal voltage is a short pulse, the capacitor can transmit the signal to the load; if the input signal is a constant voltage, the capacitor will only respond during a short transition, and then block the input signal; if the input signal is an AC signal, which is exactly in the middle of the above two situations.The higher the frequency of the AC signal, the easier it is to pass through the capacitor. We call this feature a high-pass filter function. Although the AC signal can pass through the capacitor, there will be a certain amount of clipping. This shows that the capacitor has the function of isolating DC in the steady state, and a high-pass characteristic. So we can further analyze, any circuit with capacitor and inductor, we must analyze the circuit according to the transient state and the steady state, in order to get the correct analysis result.   Ⅳ Capacitor Circuit Analysis and Calculations The analysis is available from the figure below: Figure 2. Output Voltage Usc If set Usr=10Vdc, the capacitance is equal to 10 microfarads, and the resistances R1 and R2 are both 1 kiloohm, then how to analyze the value of Usc?Step 1: Determine the time constant of the capacitor. Figure 3. Usr in Short-circuit Connection From the analysis of the above figure, it can be seen that the time constant is 20 milliseconds , and the time for 5 times the time constant is 0.1 seconds.Step 2: Let's calculate the specific value of Usc.When Usr in Figure is just established, the capacitor voltage drop is equal to zero, so there is .After 5τ, the capacitor is full of voltage, and its value is Uc=Usr, so Usc=0, .When charging starts, t=0, When the time has passed 0.1 second, we have , and the Usc at this time is almost equal to zero. Now, let's connect R1 and C in parallel, and see what happens: Figure 4. R1 and C are Connected in Parallel We see that if Usr in the figure is short-circuited, R1 and R2 are connected in parallel, so the time constant is At the beginning of Usr power on, C is equivalent to a short circuit, and Usr is directly loaded on both ends of the resistor R2, so at this time Usc=UseWhen the circuit enters a steady state, Usc is equivalent to the partial pressure of Usr by resistors R2 and R1, namely Based on this, we can derive the following equation: .In the above formula, the first term on the right side of the equal sign is the change in capacitor voltage, which reflects the transition process. The second term on the right side of the equal sign is the final steady-state voltage.Substitute the parameters, and calculate the time constant first: .In other words, when the time is 5τ, that is, 25 microseconds, the output voltage tends to stabilize. The final value is .It is still 5V, but the transition process is only 25 microseconds, which is much shorter than the previous 0.1 second.   Ⅴ FAQ 1. When a capacitor is charging in a DC circuit?At this point, the electric field between the plates cancels the effect of the electric field generated by the battery, and there is no further movement of charge. Thus, if a capacitor is placed in a DC circuit then, as soon as its plates have charged up, the capacitor effectively behaves like a break in the circuit.   2. What happens to the current in a DC circuit once a capacitor is charged?For a capacitor charge Q = capacitance C multiplied by voltage V. This quite simply means that a rate of change of voltage gives rise to a current. If the voltage is rising linearly with time, the capacitor will take a constant current and once the voltage stops changing the current is zero.   3. Does current flow in a DC circuit while a capacitor is charging?Yes. For DC circuits, when a capacitor is charged or discharged, current is flowing into and out of it. For AC circuits, a capacitor can act almost like a "resistor" but instead it is called reactance. But alas, current does flow through the capacitor.   4. Do capacitors charge with AC or DC?When DC current is applied to a circuit with only resistance and capacitance, the capacitor will charge to the level of the applied voltage. Since DC only flows in one direction, once the capacitor is fully charged there is no more current flow.   5. Can we use capacitor in DC?Capacitors can be used in many different applications and circuits such as blocking DC current while passing audio signals, pulses, or alternating current, or other time varying wave forms. ... At DC a capacitor has infinite impedance (open -circuit), at very high frequencies a capacitor has zero impedance (short-circuit).   6. Can a capacitor be charged by DC?When capacitor is connected to dc voltage source, capacitor starts the process of acquiring a charge. This will built up voltage across capacitor. Once capacitor has acquire enough charge, current starts flowing and soon capacitor voltage reaches at value approximately equal to dc source voltage.   7. Why does AC pass through capacitor but not DC?Capacitors have two parallel metallic plates placed close to each other and there is a gap between plates. A capacitor blocks DC but it allows AC. ... Therefore the electrons flowing in one direction (i.e. DC) cannot pass through the capacitor. But the electrons from AC source seem to flow through C.   8. What happens when capacitor is connected to DC?When capacitors are connected across a direct current DC supply voltage, their plates charge-up until the voltage value across the capacitor is equal to that of the externally applied voltage. ... Then the Capacitance in AC circuits varies with frequency as the capacitor is being constantly charged and discharged.   9. Why capacitor is used in DC circuit?Capacitors are useful to reduce the voltage pulsation. When the high voltage is applied to the parallel circuit, the capacitor is charged, and on the other hand, it is discharged with the low voltage. While electricity flowing out is alternating current, most of electronic circuits work with direct current.   10. Why do capacitors block DC current?We know that there is no frequency i.e. 0Hz frequency in DC supply. If we put frequency “f = 0″ in the inductive reactance (which is AC resistance in capacitive circuit) formula. If we put XC as infinity, the value of current would be zero. That is the exact reason why a capacitor block DC.   11. How is a capacitor charged in a DC circuit?When used in a direct current or DC circuit, a capacitor charges up to its supply voltage but blocks the flow of current through it because the dielectric of a capacitor is non-conductive and basically an insulator. ... At this point the capacitor is said to be “fully charged” with electrons.   12. Which capacitor is used in DC circuit?Decoupling capacitor is used, where we have to decouple the two electronics circuits. In other words, the noise generated by one circuit is grounded by decoupling capacitor and it does not affect the performance of other circuit.   13. Can you charge a capacitor with DC current?A DC voltage source is used to charge a Capacitor. When the DC voltage source is outputting more than the DC voltage source can charge, the Capacitor will charge up. Capacitors will charge up to 9 volts if they are connected to a 9-volt battery.   14. What happens if DC is applied to capacitor?When capacitors are connected across a direct current DC supply voltage, their plates charge-up until the voltage value across the capacitor is equal to that of the externally applied voltage. ... Then the Capacitance in AC circuits varies with frequency as the capacitor is being constantly charged and discharged.   15. Can we charge capacitor with DC current?When capacitor is connected to dc voltage source, capacitor starts the process of acquiring a charge. This will built up voltage across capacitor. Once capacitor has acquire enough charge, current starts flowing and soon capacitor voltage reaches at value approximately equal to dc source voltage.

IntroductionIn the landscape of modern electronics in 2025, the Zener diode remains a fundamental component for voltage stabilization and reference. Unlike standard diodes, Zener diodes are engineered to operate in the reverse breakdown region. By utilizing the specific breakdown voltage of the PN junction, they maintain a constant voltage across their terminals even when the current varies significantly.Zener diodes serve critical roles as voltage regulators, surge suppressors, and reference elements in power supply circuits. Given their importance, proper maintenance and accurate fault detection are essential skills for technicians and engineers. This guide details how to detect, test, and distinguish Zener diodes using modern troubleshooting techniques.Ⅰ How to Test Zener Diodes with Three Methods?1.1 Resistance Measurement (Basic Health Check)The resistance measurement method describes the basic health of the component—specifically, checking for shorts or open circuits. While modern digital multimeters (DMMs) are standard in 2025, analog multimeters can still be useful for this specific test due to their load characteristics.The Principle: Using an analog multimeter set to the Rx10K block (which typically uses an internal 9V or 15V battery), you can bias the PN junction.Forward Bias: Connect the red probe (negative in analog meters) to the Anode and black to the Cathode. You should see low resistance.Reverse Bias: Connect in reverse. Ideally, the resistance should be high. However, if the battery voltage exceeds the Zener voltage (e.g., a 5V Zener tested with a 9V internal battery), you will measure a resistance drop, indicating the Zener is functioning (breaking down) correctly.Using a Digital Multimeter: Set the meter to Diode Mode. Touch the probes to the diode. In one direction (forward bias), you should see a voltage drop between 0.6V and 0.8V. In the reverse direction, it should show "OL" (Open Loop) unless the Zener voltage is lower than the meter's test voltage (rare in modern DMMs). If you read 0.000V in both directions, the diode is shorted.1.2 Voltage Measurement (The Most Accurate Method)To determine the exact Zener voltage (Vz), testing the component "live" or in a test circuit is required. This is the professional standard for verifying if a Zener diode is drifting or operating within tolerance.Procedure:Connect a DC Power Supply in series with a current-limiting resistor (e.g., 1kΩ to 10kΩ) and the Zener diode (Reverse Biased).Set the power supply voltage higher than the expected Zener voltage.Use a digital multimeter in DC Voltage mode to measure across the Zener diode.Result: If the reading matches the component's rated voltage (e.g., 5.1V, 12V), the diode is healthy. If the voltage fluctuates significantly or equals the input voltage, the diode is faulty.1.3 Measuring High-Voltage Zeners (Insulation Tester)For industrial Zener diodes with high regulation voltages (above 20V or 50V), a standard multimeter's test voltage is insufficient. In these cases, a Megger (Insulation Resistance Tester) or a high-voltage DC supply can be used.Method: Connect the Megger leads to the diode (reversed). Slowly generate voltage. When the resistance reading stabilizes at a specific voltage drop, that represents the Zener breakdown voltage. Warning: Ensure the current is limited to prevent destroying the device, as Meggers can output high voltages meant for insulation testing, not semiconductor characterizing.Figure 1. Standard Zener Diode SymbolⅡ How to Measure the Leakage of Zener Diode?Leakage current is a silent killer in precision circuits. A Zener diode might pass a basic voltage test but fail under load or temperature changes due to excessive leakage.Advanced Testing: A standard multimeter cannot effectively detect minor leakage. Instead, use a Curve Tracer or an Oscilloscope with a component tester function. By applying a reverse voltage gradually, you monitor the current. A healthy Zener should conduct negligible current until it hits the "Knee Voltage." If the current rises linearly before the breakdown voltage, the diode is "leaky" (soft breakdown) and should be replaced.Ⅲ How to Figure the Polarity of the Zener Diode?Correct installation is vital. Here is how to identify the Anode (+) and Cathode (-):Visual Inspection (Through-Hole): Look for the black or blue band on the glass/plastic body. This band indicates the Cathode (-) side.Visual Inspection (SMD): On Surface Mount Devices, the Cathode is usually marked with a white bar or a chamfered edge.Multimeter Test: Set to Diode Mode. Place probes on terminals. The orientation that gives a reading (approx 0.7V) indicates the Red probe is on the Anode and the Black probe is on the Cathode.Figure 2. Zener Diode Regulator ConfigurationⅣ How to Identify Color Code Zener Diode?While many modern diodes have the part number printed directly (e.g., "5V1" or "1N4733"), older glass-passivated diodes use color bands similar to resistors.The color bands typically represent the JEDEC type number (e.g., 1Nxxxx). Alternatively, in the European BZX series, bands may denote voltage: Example: A diode with Brown (1) and Red (2) bands might represent 12V (depending on the specific manufacturer coding system). Always cross-reference with a datasheet or use a modern SMD/Component Tester (LCR Meter) to verify the breakdown voltage automatically.Ⅴ How to Distinguish Zener Diodes and Ordinary Diodes?Physically, Zener diodes and standard signal diodes (like the 1N4148) often look identical (small, glass, orange/red body with a black band).The Distinction Test: The defining characteristic is the Reverse Breakdown Voltage.Standard Diode: Will block reverse voltage up to very high limits (e.g., 100V+). Under a 12V reverse test, it acts as an Open Circuit.Zener Diode: Will conduct current when the reverse voltage exceeds its rating (e.g., 5.1V).Practical Trick: Apply 12V DC via a 1kΩ resistor to the diode in reverse. Measure the voltage across the diode. If it reads ~12V, it is likely a standard diode. If it reads a lower, stable voltage (e.g., 5.1V, 9.1V), it is a Zener Diode.Figure 3. Zener Diode Voltage Regulator CircuitⅥ FAQ1. How do you identify a 12V Zener diode?The most reliable method is to place the diode in a reverse-biased circuit with a power supply set to roughly 15V-20V and a series resistor. If the voltage across the diode clamps and stabilizes at approximately 12V, it is a 12V Zener. If you use a standard multimeter diode test, it will only show the forward voltage drop (~0.7V), which does not reveal the Zener voltage.2. How do you know if a Zener diode is bad?Common Failure Signs:Short Circuit: Reading 0Ω or 0V in both directions (most common failure).Open Circuit: Reading "OL" in both directions.Drift: The diode regulates voltage, but at the wrong value (e.g., a 5V Zener regulating at 3V or 8V).3. What is the difference between a rectifier diode and a Zener diode?A standard rectifier diode is designed to conduct current in only one direction (Forward Bias) and block voltage in the reverse direction. A Zener diode is designed to conduct in the forward direction like a normal diode, but also safely conduct in the reverse direction once a specific voltage threshold (Zener Voltage) is reached.4. What happens when a Zener diode is shorted?When a Zener diode fails short, it acts like a straight piece of wire. It allows maximum current to flow in both directions with zero resistance. In a power supply circuit, this usually causes the fuse to blow or the series resistor to overheat and burn out immediately.5. Can I test a Zener diode in-circuit?In-circuit testing is often inaccurate due to parallel components (capacitors or other resistors) affecting the reading. However, you can check for a dead short. If you measure 0Ω across the Zener while it is on the board, it is likely dead. For accurate voltage testing, lift one leg of the component off the PCB.6. Why is a Zener diode used in reverse bias?Zener diodes are heavily doped. This doping creates a very thin depletion region that allows electrons to tunnel across the junction when a specific reverse voltage is applied (Zener Effect). This property is what provides the stable reference voltage required for regulation.7. What happens if you forward bias a Zener diode?If you connect a Zener diode in forward bias (Anode to Positive), it behaves exactly like a standard silicon diode. It will conduct current with a voltage drop of approximately 0.7V. It does not provide voltage regulation in this orientation.8. How do I identify an SMD Zener diode?SMD (Surface Mount Device) Zeners are often too small for full part numbers. They use Marking Codes (typically 2 or 3 alphanumeric characters). You must look up this code in an "SMD Codebook" or datasheet to identify the voltage rating. Visually, they often come in SOT-23 (3-leg) or SOD-123 (2-leg) packages with a band marking the cathode.

IntroductionIn electronics, the diode has the unique characteristic of unidirectional conduction. The main functions are rectification, voltage stabilization, and detection. In addition, there are light-emitting diodes(LED) added with different materials for indication and illumination. In a diode circuit, current can only flow in from the anode and flow out of the cathode. According to different circuit requirements, there are many different types of diodes to choose from. Most of the early diodes were made of germanium single crystals. Later, with the solution of silicon materials and manufacturing processes, silicon tubes have been developed and popularized. Here's how to distinguish silicon(Si) diodes and germanium(Ge) diodes.CatalogIntroductionⅠ Circuit Properties: Si Tube vs Ge Tube1.1 Differences between Ge and Si Diode1.2 Differences between Ge and Si Transistor1.3 SummeryⅡ Common Diode Types UsesⅢ Common Transistor Models UsesⅣ New Development: SiC Schottky Diodes4.1 SiC Schottky Diode Basic4.2 SiC Tech Characteristics4.3 SiC Schottky Diode ApplicationsⅠ Circuit Properties: Si Tube vs Ge Tube1.1 Differences between Ge and Si DiodeThe circuit properties of Si diodes and Ge diodes are the same, and the manufacturing process is also the same. Due to the difference in materials, the thermal stability of Si diodes is good, and the thermal stability of Ge diodes is slightly poor.1) When the current is the same, the DC resistance of the Ge tube is smaller than that of the Si tube. However, as for AC resistance, the situation is opposite.2) According to experimental research, the Ge diode starts to have current at 0.2V in the forward direction, while the Si diode does not start to have current until 0.5V, that is to say, the initial voltages for the two to reach conduction are different.3) Under reverse voltage, the leakage current of silicon tube is much smaller than that of germanium tube. After the start of conduction, the Ge tube current increases slowly, and the Si tube current increases relatively quickly.4) The threshold voltage of silicon tube is higher than that of germanium tube, because the threshold current of silicon tube is much smaller than that of germanium tube. Generally, the threshold voltage of a silicon tube is about 0.5V~0.6V, and the threshold voltage of a germanium tube is about 0.1V~0.2V.5) Temperature changes have a greater impact on Ge diodes, but less on silicon diodes. Therefore, silicon tubes have better high temperature resistance than Ge tubes.6) Forward voltage required for diode conduction:Diode TypesForward Conduction VoltageSi0.7VGe0.15VIt can be seen from the above table that the forward voltage required for the silicon tube to be turned on is higher than that of the germanium tube, so the diode can be distinguished by knowing the forward voltage.In addition, there is a very direct method to measure your diode with the Ω barrier of a multimeter. As shown in the figure, the red pen (anode) of the multimeter is connected to the cathode of the diode, and the black pen (cathode) is connected to the anode of the diode. If the resistance of the tested diode is around 1kΩ, it is a germanium tube; if the resistance is 4~8kΩ, it is a silicon tube.Compared with germanium diodes, silicon diodes have higher voltage resistance, shorter response time, and stable performance. In most circuits, silicon tubes can replace germanium tubes, but its forward pressure drop is higher than that of germanium tubes. Therefore, in some specific environments, such as small signal detection circuits, germanium tubes are better.1.2 Differences between Ge and Si TransistorThe main difference is that the junction voltage drop is different, the forward voltage drop of the germanium tube is lower about 0.3V, and the silicon tube is higher about 0.7V. In addition, silicon materials are abundant and manufacturing processes are suitable for mass production, so they are widely used and become the protagonist of electronic devices.Germanium semiconductor materials have high electron mobility and are suitable for low-voltage and high-current devices, but the temperature characteristics of it is worse than that of silicon materials. The reverse leakage current of PN junctions is much larger than that of silicon materials. Therefore, silicon tubes have to be used in high-power devices and high back-pressure devices. The triode has two PN junctions. In terms of a PN junction, the forward voltage of the PN junction of the germanium tube is reduced to only 0.3V, while the silicon tube is 0.7V. The reverse withstand voltage germanium tube is very low, so it is easy to reverse breakdown. Therefore, the penetrating current of the Ge tube is relatively large, noise will be generated in the amplifying circuit, and it is easy to be damaged. 1.3 SummeryGermanium diodes was used a lot in early electronics, such as radios, but they have largely been replaced by silicon diodes. Because the structure of germanium crystals will be destroyed at higher temperature, while Silicon crystals are not easily damaged by excess heat. What's more, peak inverse voltage ratings of silicon diodes are greater than germanium diodes. As for price, Silicon material has low cost and its producibility of high quality silicon dioxide needed for impurity diffusion and surface passivation processes. Therefore, germanium tubes were only produced before the 1970s. Ⅱ Common Diode Types Uses① Zener DiodesThe Zener diode is also made of a PN structure. It is in the reverse breakdown state when working (the ordinary diode will be damaged in the reverse breakdown zone). When connected to the circuit, it should be reversed, that is, the anode of the Zener diode should be connected with the cathode of the voltage stabilizing circuit, so is the rest. The voltage stabilizing tube uses its reverse breakdown current to change in a wide range, the reverse breakdown voltage is basically unchanged, to achieve the purpose of voltage stabilization.② Light-emitting DiodesThe light-emitting diode emits light when it passes forward current, and has the performance of electro-optical conversion. The visible light includes red, yellow, green, blue, purple, etc. It is widely used in various electronic equipment as working status indicator.③ PhotodiodesThe reverse current of the photodiode increases with the increase of the light intensity. Its main feature is: the tube works in the reverse state, and the reverse current is proportional to the illuminance.④ Rectifier Diodes for AutomobilesThe working principle of the diode for automobile silicon rectifier generator is basically the same as that of other diodes, but the external structure is different from that of general diodes. It has one lead pole and the other pole is a shell. It is divided into two types: positive diode and negative diode. The terminal is the positive pole and the shell is the negative pole, while the leading end of the negative diode is the negative pole and the shell is the positive pole. In order to facilitate identification, the positive diode is usually coated with a red dot and the negative diode is coated with a black dot.⑤ Freewheeling DiodeFreewheeling diodes are common used in automobiles. In addition, fast recovery diode (a kind of semiconductor diode with good switching characteristics and short reverse recovery time) is mainly used for switching power devices (such as IGBT or MOSFET) of various power converters to play a freewheeling effect. Ⅲ Common Transistor Models UsesThe following table lists some commonly used transistor models and their main parameters, packages and alternative models.ModelBasic ParametersDescriptionPcVCBOVCEOVEBOhFEIC2SC2655(NPN, TO-92L)0.9W50V50V5V*2AHigh-speed switching tube, used for high-current PWM push-pull drive, complementary to the 2SA10202SC9013(NPN, TO-92)0.625W40V20V5V84-2020.5AComplementary to  the SS90122N5551(NPN, TO-92)0.63W180V160V6V30-2500.3AHigh voltage tube, complementary to the 2N5401KSP2222A(PN2222A)(NPN, TO-92)0.625W75V40V6V35-30006AUniversal switch type, complementary to the KSP2907AS8050(NPN, TO-92)0.625W40V25V5V50-3000.5AComplementary to the S8550BD681A(NPN, TO-12640W100V100V5V750-15004ACan drive large relays, Darlington tubeTIP41/A/B/C(NPN, TO-220)60W40~100V40~100V5V15-756AMiddle Power tubes, complementary to the TIP42, can be used for IGBT PWM driveMPSA44(NPN, TO-92)0.625W500V400V6V40-3000.3AHigh voltage tubeKSP2907A(PNP, TO-92)0.625W-60V-60V-5V50-3000.6ACommon-type, complementary to the KSP2222AS8550(PNP, TO-92)0.625W-40V-25V-5V50-3000.5AComplementary to the S80502SA1020(PNP, TO-92L)0.9W-50V-50V-5V40-2402AHigh-speed switch tube, complementary to the 2SC26552SA684(PNP, TO-92L)1W-60V-50V-5V50-3401ADarlington tubeTIP42/A/B/C(PNP, TO-220)65W-40~-100V-40~-100V-5V15-756AMiddle power tubes, complementary to the TIP41, can be used for IGBT PWM driveKSP94(PNP, TO-92)0.625W-400V-400V-6V40-3000.3AHigh voltage tubeⅣ New Development: SiC Schottky Diodes4.1 SiC Schottky Diode BasicSchottky diodes, also known as hot carrier diodes, form a Schottky barrier through metal and semiconductor contacts to achieve rectification. Compared with ordinary PN junction diodes, the reverse recovery inertia of it is very low. Therefore, Schottky diodes are suitable for high-frequency rectification or high-speed switching.Silicon carbide (SiC) is a high-performance semiconductor material, so SiC Schottky diode have advantages of higher energy efficiency, higher power density, smaller size and higher reliability. It can be used in power electronics to break the limit of silicon, and becomes the preferred device for new energy and power electronics.4.2 SiC Tech CharacteristicsSiC is a compound semiconductor composed of silicon and carbide. It provides a number of advantages over silicon. The band gap of SiC is 2.8 times that of silicon (wide band gap), reaching 3.09 eV. Its insulation breakdown field strength is 5.3 times that of silicon, up to 3.2MV/cm, and its thermal conductivity is 3.3 times that of silicon, about 49w/cm·k. Like silicon semiconductor materials, it can be made into junction devices, field-effect devices, and special Schottky diodes. Here is SiC characteristics:1) Silicon carbide single-carrier devices have a thin drift region and low on-state resistance, about 100-300 times smaller than silicon devices. Due to the small on-resistance, the forward loss of the silicon carbide power device is small.2) The silicon carbide power device has a high breakdown voltage due to its high breakdown electric field. For example, the voltage of commercial silicon Schottky diode is less than 300V, while the breakdown voltage of the first commercial SiC Schottky diode has reached 600V.3) SiC has higher thermal conductivity.4) SiC devices can work at higher temperatures, while the maximum operating temperature of Si devices is only at 150ºC.5) SiC has high resistance to radiation.6) The forward and reverse characteristics of SiC power devices vary little with temperature and time, and their reliability is good.7) SiC devices have good reverse recovery characteristics, with low reverse recovery current and switching loss.8) SiC devices can reduce the volume of power devices and circuit losses.4.3 SiC Schottky Diode ApplicationsSiC Schottky diodes can be widely used in medium and high power fields such as switching power supplies, power factor correction (PFC) circuits, uninterruptible power supplies (UPS), photovoltaic inverters, etc., which can significantly reduce circuit losses and improve circuit operating frequency.Substituting SiC SBD(Schottky barrier diodes) for the original silicon FRD(fast recovery diodes) in the PFC circuit can make the circuit work above 300kHz, and the efficiency remains basically unchanged, while the efficiency of the circuit using silicon FRD above 100kHz drops sharply. As the operating frequency increases, the volume of passive components such as inductors decreases correspondingly, and the volume of the entire circuit board decreases by more than 30%. Frequently Asked Questions about Silicon and Germanium Diodes1. Why silicon diode is better than germanium diode?The structure of Germanium crystals will be destroyed at higher temperature. However, Silicon crystals are not easily damaged by excess heat. Peak Inverse Voltage ratings of Silicon diodes are greater than Germanium diodes. Si is less expensive due to the greater abundance of element. 2. How can I tell if I have a Ge or Si diode?You can easily distinguish Silicon and Germanium Diodes. Silicon diodes should read approx 0.7V and Germanium diodes should read 0.3V. A little difficult to distinguish Schottky diodes though. They should show approx 0.2V which is close to 0.3V. 3. What are the differences between silicon and germanium semiconductor?The key difference between silicon and germanium is that the Germanium has d electrons, but Silicon does not have any d electrons. Silicon and germanium, are both in the same group (group 14) of the periodic table. Hence, they have four electrons in the outer energy level. 4. What is difference between silicon and germanium?Silicon and germanium have four valence electrons but at the given temperature germanium will have more free electrons and higher conductivity than silicon. Silicon is more widely used in the electronic device than germanium since it can be used at a higher temperature. 5. What is the difference between silicon and germanium transistors?To answer you actual question, there are two significant differences between silicon and germanium transistors: germanium has a low melting point and germanium transistors have much less tolerance for high temperatures. The forward voltage drop of a germanium junction is lower than for silicon.