The Kynix Blog

IntroductionThe audio power amplifier is a device used to drive the speaker to produce sound, thereby reproducing the sound. It is used in all electronic products that produce sound, which amplifies the smaller audio signal, increases its power, and then outputs it. Pre-amplification mainly used for small signals, and amplifies the voltage of the input audio small signals by using a non-inverting amplifier circuit to obtain the input required by the latter stage. The latter stage mainly amplifies the power so that it can drive the resistor to obtain the required audio.Making an Audio Power AmplifierCatalogIntroductionⅠ What is Power Amplifier Distortion?Ⅱ Types of Audio Power Amp Distortion2.1 Harmonic Distortion (THD)2.2 Intermodulation Distortion (IMD)2.3 Transient Distortion 2.4 AC Interface DistortionⅢ ConclusionⅣ FAQⅠ What is Power Amplifier Distortion?Distortion is the phenomenon that the input signal and the output signal change in the amplitude proportional relationship, phase relationship and waveform shape. The distortion of audio power amplifiers is divided into electrical distortion and acoustic distortion. The former is caused by the circuit, and the latter is caused by the speaker of the sound reproduction device. The types of electrical distortion are: harmonic distortion, intermodulation distortion, and transient distortion. The acoustic distortion is mainly the distortion of the AC interface. According to the nature, there are nonlinear distortion and linear distortion.Linear distortion refers to the change in the amplitude and phase relationship between signal frequency components, and only the amplitude and phase distortion of the waveform appear. The characteristic of it is that no new frequency components are generated.Figure 1. Linear DistortionNon-linear distortion means that the signal waveform has been distorted and new frequency components have been generated.  Ⅱ Types of Audio Power Amp DistortionThe main points of distortion produced by audio power amplifiers are as follows:2.1 Harmonic Distortion (THD)🔸What is THD?This distortion is caused by non-linear components in the circuit. After the signal passes through these components, new frequency components (harmonics) are generated, which affect the original signal. The characteristic of this distortion is the input signal waveform inconsistent with the shape of the output signal. That is, the waveform is distorted. The following is a specific analysis.Harmonic distortion refers to the more harmonic components of the output signal than the input signal. It is caused by a system that is not completely linear. The sum of all additional harmonic levels is called total harmonic distortion, which is related to frequency. Generally speaking, at a frequency of 1000Hz, the distortion is the smallest. So many products confirm the distortion at this frequency as a indicator.Harmonic distortion is actually the distortion of the sound when the speaker reproduces the sound due to the resonance phenomenon that occurs during the working process of the speaker. Although only the fundamental frequency signal in the speaker is the original sound signal, due to the inevitable resonance phenomenon (the second, third and even multiple harmonics are generated on the basis of the original sound wave), there is no longer only the fundamental frequency signal in the sound signal, but also includes harmonics and their frequency multiplier components. These frequency multiplied signals will cause distortion when the speaker is playing. For ordinary speakers, a certain harmonic signal component is allowed, but it must be a prerequisite that it does not have a large impact on the sound fundamental frequency signal output.The total harmonic distortion usually expressed as a percentage. Generally speaking, the smaller the value, the better. Generally speaking, the THD value of high-quality equipment is very low (less than 0.002%), but there are exceptions. Many electronic tube devices have very high THD, but transistor devices must have low THD because their excess harmonics can make the sound uncomfortable.🔸How to Calculate THD?In the above formula, G represents the effective value of the harmonic component. It will be replaced by I when expressing current and U when expressing voltage as required. The value of H is given in each standard related to the limit. According to the above definition, THD does not include interharmonics, and there is a fixed upper limit of harmonics.In the above formula, Q is the total effective value, and Q1 is the fundamental effective value, which can represent the voltage or the current. According to the above definition, THD includes interharmonics and DC components.🔸How to Reduce THD?The main ways to reduce harmonic distortion are: 1) Apply an appropriate amount of negative feedback. 2) Choose amplifiers with high characteristic frequency, low noise figure and good linearity. 3) Increase the power reserve of the power supply and improve the filtering performance of it. 2.2 Intermodulation Distortion (IMD)🔸What is IMD?This distortion is usually produced by active devices in the circuit (such as transistors and tubes). Two or more signals of different frequencies pass through an amplifier or speaker to produce beats and form new frequency components. The magnitude of the distortion is related to the output power. Since these newly generated frequency components have no similarity with the original signal, the less intermodulation distortion is also easy to be noticed by the human ear.🔸How to Calculate IMD?The excitation signal used in the measurement technique of IMD is more than a single simple sinusoidal signal. In the fields of professional audio, broadcasting and consumer audio, two sine waves are used as excitation signals to measure it. When any two sine signals with frequencies of F1 and F2 are applied to the nonlinear device, the original two sine waves will be generated plus countless IMD terms, that is, countless combined frequency components, as shown in the following formula: mF1±nF2Where m and n are any positive integers. The order of any particular IMD value is the sum of m and n. The order of some terms are listed below:F1-F2 2nd order (even order)F1+F2 2nd order (even order)2F1-F2 3rd order (odd order)F1-2F2 3rd order (odd order)2F1+F2 3rd order (odd order)3F1-F2 4th order (even order)3F1+2F2 5th order (odd order)…….The above "odd" and "even" refer to whether m+n is odd or even.The measurement method of IMD is actually the measurement of harmonic voltage components, and its formula is:Where, F1 is high frequency, F2 is low frequency.🔸How to Reduce IMD?Methods to reduce intermodulation distortion: 1) Use electronic frequency division to limit the working bandwidth of the amplifier circuit or loudspeaker, thereby reducing the generation of beats. 2) Choose a tube or circuit structure with good linearity. 2.3 Transient Distortion Transient distortion is an important indicator of modern acoustics. It reflects the ability of the power amplifier circuit to keep track of transient signals, so it is also called transient response. This kind of distortion makes music lack level or transparency, and there are two forms of expression:🔸A. Transient Intermodulation Distortion (TIM)When inputting a pulsed transient signal, the output terminal cannot get the proper output voltage immediately due to the capacitance in the circuit, and the negative feedback circuit cannot get a timely response. The amplifier is in an open loop state at this moment, making the output instantaneous. Clipping occurs due to overload. This clipping distortion is called transient intermodulation distortion, and it is more serious on transistor machines.Transient intermodulation distortion is a dynamic indicator of the power amplifier, which is mainly caused by the deep negative feedback inside the power amplifier. It will affect the sound quality of the stone machine and cause "transistor noise" and "metal noise".The main methods to reduce this distortion are as follows: 1) The TIM can be eliminated by controlling the gain within the delay time of the negative feedback amplifier. 2) Multistage negative feedback can be used, so it is not easy to cause TIM due to fast feedback time and short path.3) Take well anti-interference measures.🔸B. Distortion Caused by Too Low Conversion RateAs mentioned above, high-level input pulses cause the amplifier to clip and then cause transient intermodulation distortion. Will low-level input pulses cause distortion? It depends on the response time of the amplifier. Because the response time of the amplifier is too long, the change of the output signal of the amplifier cannot keep up with the rapid change of the input signal. The transient distortion is caused by the low conversion rate. It reflects the response speed of the amplifier to the signal. This low-distortion amplifier has very good sound quality resolution, layering and positioning. 2.4 AC Interface DistortionThe distortion of the AC interface is caused by the back EMF of the speaker (the electric potential generated by cutting the magnetic lines of force when the speaker sounds vibration) feedback to the circuit.The improving methods are:1) Reduce the output impedance of the circuit.2) Choose a suitable speaker to make the damping coefficient more reasonable.3) Reduce the internal resistance of the power supply. Ⅲ ConclusionFor different types of audio power amplifiers, due to the differences the circuit itself, their sound is different. Transistor power amplifiers are affected by odd harmonic distortion and transient intermodulation distortion, and the sound will be cold, straightforward, burr or metallic. The sound of the tube amplifier is warm, thick, and stretched. So far, the electronic tube is still the active amplifier device with the best linearity and the smallest native distortion, and the transistor cannot be compared. But in fact, the total harmonic distortion (THD) of the tube power amplifier is several orders of magnitude larger than that of the transistor power amplifier. This is because it is difficult to add sufficient negative feedback to improve the linearity of the tube power amplifier. Most of these non-linear distortions are even harmonics that are pleasing to the ears, but they make people feel pleasant to the ears. The transistor power amplifier uses a large loop deep negative feedback to significantly improve the linearity. Due to the stability requirements, a compensation capacitor is introduced as the main pole. However, it may cause a problem of poor transient response. With the advancement of technology, the sound quality of integrated chip audio power amplifiers is getting closer and closer, even surpassing the above two types of power amplifiers, and it also has obvious advantages in terms of volume, cost, and scope of application. Ⅳ FAQ1. What is power amp distortion?The short answer is that power amp distortion derives from overloading/distorting an amplifier's power section. After the preamp portion of an amplifier is 'done' with the signal, it is then passed on to the phase inverter and out to the amp's power tubes. 2. Why is my amp distortion?You can create distortion by merely increasing the volume of your guitar and setting the input gain high enough on your amplifier. This combination of volume and preamp gain will create distortion as explained above, the gain exceeding the voltage capacity, causing the sound waves to clip. 3. Is amp distortion better than pedal distortion?Distortion pedals are considered more versatile with more parameters to shape your ideal sound. Their downfall is that some cheap pedals can sound unnatural. In contrast, the majority valve amp distortion provides a more, smoother, and overall, more well-rounded distortion. 4. How do I adjust the distortion on my amp?Turn knobs marked "gain" or "overdrive" all the way up. Turn other volume knobs down to get the loudness you want. Once you've proved you can get heavy distortion, dial things back to find the tone you want. Some amps won't distort at low volumes. 5. Do amps have built in distortion?The answer to the question do all guitar amps have distortion is no; not all guitar amps have distortion. In fact, there are different categories you could place guitar amps in depending on how they generate their distortion. 6. Does preamp reduce distortion?Preamp distortion generally offers higher gain than power amp distortion and is more compressed and smoother, with higher sustain at lower volume levels. ... In general, vintage-style amps sound best when driven into power amp distortion — depending on the amp, its preamp may not even be able to distort. 7. Do tube amps need distortion pedals?Most tube amps won't need a distortion pedal, digital or otherwise. When an amp has both a dirty (gain) and a clean channel, this allows you to dial your distorted tones along with whatever clean sound you might want to use. 8. Can you use a distortion pedal without an amp?Most modern multi-effects pedals have a jack where you can plug in any speakers or headphones. This means you can play an electric guitar without an amp by using a multi-effects pedal. Simply plug your guitar into a suitable multi-effects pedal and plug headphones or speakers into the pedal. 9. What amp is good for distortion?Top 5 Amps for Creating Clean and Distortion Sounds1) Orange Micro Terror2) Blackstar HT1R3) Peavey Vypyr VIP 14) Fender Champion 205) Marshall MG50CFX 10. Why is my audio distorted?The most common reason for distortion is an input overload like the microphone overload mentioned above. Mic'ing an instrument, or even a vocal, is more than sticking a microphone right up to the sound source. ... A distorted sound can be resolved by placing a greater distance between the sound source and the microphone.

Ⅰ Introduction A Bluetooth transmitter is a device that sends data between two Bluetooth devices. A Bluetooth transmitter operates by decoding the source file into a format that is then transferred via radio waves to the Bluetooth device. Bluetooth transmitters may now connect to a broad variety of devices, including headphones and speakers. this video shows some basic information about bluetooth transmitter Bluetooth is not supported by all gadgets. A Bluetooth transmitter would be required to make one compatible. This is a gadget that allows televisions and home theater systems to broadcast high-definition audio to headphones and speakers. In other words, a transmitter sends out a Bluetooth signal that may be controlled by a compatible device, such as a smartphone or tablet. It operates by connecting to a device's digital or analog output and transmitting a signal to specific Bluetooth devices. It's fantastic for listening to your favorite movies or TV shows without bothering those around you. Because you can wirelessly connect your headphones to the television, you can roam around your house while still watching the show. CatalogⅠ IntroductionⅡ Types of Bluetooth Transmitters2.1 Wired Bluetooth Transmitters2.2 Wireless Bluetooth TransmittersⅢ Bluetooth Transmitter VS Bluetooth Receiver3.1 The Range of a Receiver and Transmitter3.2 Do Receivers and Transmitters Distort Sound Quality?3.3 Do Receivers and Transmitters Interfere With Other Devices?3.4 Which Is Better: Bluetooth Receiver or Transmitter?Ⅳ Consider These Factors When Purchasing a Bluetooth Transmitter4.1 Dual Function Technology4.2 Battery Life4.3 Controls4.4 Sound Output4.5 Device Pairing Capabilities4.6 Transmission Range4.7 Ease of ConnectionⅤ Applications and Usages of Bluetooth Transmitter5.1 Bluetooth Transmitter for Car5.2 Bluetooth Transmitter for TV5.3 Bluetooth Transmitter for PCⅥ Frequently Asked Questions About Bluetooth Transmitter Ⅱ Types of Bluetooth Transmitters2.1 Wired Bluetooth TransmittersThis sort of transmitter, as the name implies, employs a wire to connect two devices. While they are simple to connect, having a device-compatible adaptor is required. Wired Bluetooth transmitters are likewise less popular than wireless Bluetooth transmitters. 2.2 Wireless Bluetooth TransmittersWireless Bluetooth transmitters, on the other hand, are more advanced. Some variants include antennae for wireless data transmission. Others are pocket-sized, which means they are more convenient. They can connect to devices without the use of adapters, making them many people's first pick. Ⅲ Bluetooth Transmitter VS Bluetooth ReceiverA receiver receives a Bluetooth signal and uses it to stream audio from an existing non-compliant Bluetooth device. A Bluetooth receiver can be connected to your preferred analog or digital audio system, allowing you to stream music and podcasts from your phone to the speaker. this video shows the difference of bluetooth transmitter and receiver This can turn any audio system wireless, transforming it into a Bluetooth-controllable device. This means that you can obtain the high-quality sound you want from digital or analog systems while still reaping the benefits of wireless communication. 3.1 The Range of a Receiver and TransmitterThe early Bluetooth devices could only send signals within a 10-meter (32-foot) range. When you consider that walls and obstructions can reduce this signal, it suggests you didn't have a lot of movement. However, as newer versions of Bluetooth were released, it became easier to carry audio signals across longer distances. Most wireless receivers and transmitters currently have a range of 30 meters, or around 100 feet. This allows you to listen to music or watch TV from a room or two down the corridor. 3.2 Do Receivers and Transmitters Distort Sound Quality?Since its inception in the late 1990s, Bluetooth has come a long way. Audio data can now stream further and quicker than ever before thanks to the most recent update. However, when employing receivers or transmitters, the sound characteristics can alter as a result of the use of a secondary source. One of the most common problems with Bluetooth receivers is that the music is delayed from its source. While this isn't generally evident when listening to music, it can be annoying when watching a movie or television show. This is due to the fact that the characters' lips frequently appear to be out of sync with their conversation. It is critical to purchase a receiver or transmitter that employs low latency technology, as this reduces the length of time it takes for the signal to reach the device. Standard Bluetooth audio takes 170-270 ms, therefore you'll want a device that just takes 30-40 ms to avoid synchronization troubles. Furthermore, as compared to corded headphones, Bluetooth headphones can have inferior sound quality. Consider using a Bluetooth amplifier to maintain wired quality while also delivering the convenience of Bluetooth. With LDAC audio coding technology, this can convert any wired headset into a Bluetooth compatible device while also improving the original audio quality. 3.3 Do Receivers and Transmitters Interfere With Other Devices?Some Bluetooth receivers and transmitters may lose signal or cross signals with other Bluetooth devices in the proximity. Wi-Fi can potentially interfere with the strength of your Bluetooth signal. If you're looking for one of these devices, make sure it has a high interference tolerance. This is often accomplished with a chip set that supports 24-bit audio and employs aptX HD, as this provides a considerably more steady signal, particularly in places with a lot of interference. 3.4 Which Is Better: Bluetooth Receiver or Transmitter?It's less a matter of which is better in general and more about which works best for you. Both of these goods offer incredible features that will be extremely useful in your daily routines. If you have an antique stereo system that you adore for its design or sound quality, a Bluetooth receiver is the way to go. This is one of the finest ways to make any wired stereo Bluetooth compatible, so you can listen to music from Spotify or Apple Music on a stereo that ordinarily only accepts tapes or LPs. If you wish to stream sound from a device that isn't Bluetooth compatible, such as your television, you'll need to get a Bluetooth transmitter. This is ideal if you recently purchased a high-end wireless speaker system but require a way to stream sound from your television. It's also ideal if you prefer listening to music using headphones. Receivers and transmitters are essential tools for Bluetooth technology, and much more so for audiophiles who appreciate high-quality sound. While there are some parallels between the two, the fundamental difference is that a receiver receives Bluetooth signals while a transmitter sends them out. Receivers are ideal for streaming music to your favorite wired audio system, while transmitters are ideal for transferring Bluetooth sound from a television to wireless audio devices. You might also purchase an amplifier to enhance the audio quality of corded headphones. Regardless of which product you choose, you will have an unrivaled enjoyment of your favorite media. Ⅳ Consider These Factors When Purchasing a Bluetooth TransmitterThere are numerous Bluetooth transmitters available on the market. Here are the precise factors to consider when purchasing a Bluetooth transmitter to assist you choose the ones that best suit your needs. 4.1 Dual Function TechnologyWhen purchasing a Bluetooth transmitter, the first thing to consider is its functioning. Many Bluetooth transmitters can also function as Bluetooth receivers (we'll go through transmitters and receivers in more detail later). While all Bluetooth transmitters can send music to your headphones or speakers, some may also receive audio from your device and send it to your headphones or speakers. 4.2 Battery LifeThis section only relates to Bluetooth transmitters that are cordless or portable. Lengthy battery life means you'll be able to use the transmitters on long excursions or for days without needing to charge them constantly. This also means that the transmitter will most likely be available whenever you need it. A Bluetooth transmitter with a long battery life can last for at least 8 hours. Anything less than that may not be ideal, especially if the transmitter must be used outside. 4.3 ControlsBluetooth transmitters are simple devices, although the controls differ greatly between types. Some transmitters have only one universal button and light, whilst others have several buttons and lights. Contrary to popular assumption, those with several buttons and lights are less difficult to use because they do not confuse you. 4.4 Sound OutputAlthough Bluetooth transmitters can transport information, they are most typically used to link audio devices such as headphones and speakers. Given this, it's critical that you listen to the transmitter's audio output. Unfortunately, some Bluetooth transmitters limit sound volume or quality. To test the sound output of a transmitter, the volume control (if present) must first be adjusted to maximum. You can then compare its sound to that of your headphone set or speaker when connected by wire or another Bluetooth transmitter. 4.5 Device Pairing CapabilitiesSome Bluetooth transmitters can only send data to one device at a time. Others, on the other hand, can connect to numerous devices at the same time (for example, your headphones and your roommates'). Bluetooth transmitters that can connect to numerous devices are clearly superior than those that can only connect to one device. They can help you save money because you won't have to buy a Bluetooth transmitter for every non-Bluetooth gadget you own. 4.6 Transmission RangeThe transmission range is the maximum distance a Bluetooth transmitter can work if there are no objects interfering with the signal. Bluetooth transmitters are categorized based on their broadcast range. Class 1 has a range of roughly 100 meters, whereas Class 2 has a range of up to 10 meters. Class 2 is the most prevalent class on the market, and it is adequate for residential use. However, if you want a longer transmission range, investing a few dollars more with a Class 1 transmission is worthwhile. 4.7 Ease of ConnectionTrying out a Bluetooth transmitter, or any device for that matter, is essential before purchasing. Of course, you must first link it with the devices you use the most regularly. Some Bluetooth transmitters, according to my experience, instantaneously couple with devices, while others do not (even after repeated attempts). Although Bluetooth pairing can be difficult at times, you need a Bluetooth transmitter that can couple with your devices consistently and smoothly. Ⅴ Applications and Usages of Bluetooth Transmitter5.1 Bluetooth Transmitter for CarIf you wish to utilize a Bluetooth transmitter to connect your car's music system to your smartphone, follow these instructions. 1)As with TVs, you must first locate a Bluetooth FM transmitter compatible with your car's audio system.2)Connect the Bluetooth transmitter to your vehicle to activate it.3)Enable Bluetooth on your smartphone and pair it with the transmitter.4)You must next adjust your car's radio to an empty FM frequency. This is necessary since a radio station's channel may interfere with your phone calls.5)On the Bluetooth transmitter, select the same empty channel. That's all. You can now listen to music or make phone calls using your car's audio system. 5.2 Bluetooth Transmitter for TVIf you wish to utilize a Bluetooth transmitter to link your TV to your wireless headphones or speaker, follow these steps. 1)You may wish to begin by purchasing a Bluetooth transmitter that is compatible with your television.2)To switch on the Bluetooth transmitter, connect it to a power supply. If it has its own battery, all you have to do is switch it on.3)After turning on the transmitter, connect it to the audio output of your television.4)After that, you must pair your Bluetooth-enabled device with the transmitter. It's best if you can get close to the transmitter while doing this to ensure a smooth connection.5)There you have it. Once associated, you can use your Bluetooth device to listen to your TV. 5.3 Bluetooth Transmitter for PCIf you wish to utilize a Bluetooth transmitter to link your PC to your smartphone, speakers, or headphones, follow these steps. Bluetooth is built into the majority of PCs. It is the older ones who aren't. First, ensure that your PC does not have Bluetooth. 1)As with the previous gadgets, you must first locate a Bluetooth transmitter that is compatible with your computer. 2)Connect your Bluetooth transmitter to your PC.3)Install the transmitter after connecting it to your PC. Typically, an installer will appear on your screen. When the installer appears, run it. 4)Connect your Bluetooth device to the Bluetooth transmitter.5)There you have it. After you've associated your Bluetooth headphones or speakers, you're ready to transfer files to or from your PC, watch videos, or listen to music. Ⅵ Frequently Asked Questions About Bluetooth Transmitter1. How Does a Bluetooth Transmitter Work?They convert wired audio signals to wireless audio signals, which they then "transmit" to your Bluetooth headphones or speakers. To put it another way, they "add" Bluetooth audio capability to non-Bluetooth devices. 2.Can a Bluetooth transmitter connect to a Bluetooth receiver?Simply connect your Bluetooth-enabled phone, PC, or tablet to the receiver, the transmitter unit to Bluetooth headphones or speakers, and the 3.5mm cable to both the transmitter and receiver. This extends the reach of your music across your home. 3.How do I reset my Bluetooth transmitter?Transmitter/Receiver Device Reset:1)Ensure that the device is turned off.2)Switch the TX/RX switch to the opposite position.3)Power on the device.4)When the device begins to flash red and blue, switch it off.5)Return the switch to its original TX or RX position. 4.Why is my Bluetooth transmitter not connecting?Previous linked devices can be remembered by the Bluetooth transmitter. If the transmitter is unable to couple with your Bluetooth device, delete the pairing history by pushing the Power Button twice while the transmitter is turned on until the LED indicator alternately flashes red and blue. The transmitter should then be restarted to couple again. 5.Do I need a transmitter for wireless headphones?If you have Bluetooth headphones, all you truly need is a Bluetooth transmitter. Transmitters can be purchased for as little as $15 online or at your local electronics store. Essentially, it converts the 3.5mm or RCA output from your television into a Bluetooth signal. 

Introduction Operational amplifiers will oscillate in many practical applications. For example, there are many kinds of loads that will cause them to oscillate. A feedback network that is not properly designed can cause them to become unstable. Insufficient power supply bypass capacitors may also make them unstable. Even the input and output may oscillate into a single-port system. This article will tell some common causes that cause the op amp to oscillate and the corresponding countermeasures. Catalog Introduction Ⅰ Basic Op Amp Circuits Ⅱ Example: LTC6268 Amplifier Ⅲ Decompensated Amplifiers Ⅳ Feedback Network Ⅴ Load Problem Ⅵ Strange Impedance Ⅶ Power Ⅷ Conclusion Ⅸ FAQ Ⅰ Basic Op Amp Circuits Figure 1. shows a block diagram of a non-rail-to-rail amplifier. The input controls the gm box, which drives the gain node and is buffered at the output. The compensation capacitor Cc is the main frequency response component. The return pin of Cc should be grounded, if there is such a pin and the op amp is not grounded, the capacitor current will return to one or two power supplies. Figure 1. Block Diagram of a Non-Rail-to-Rail Amplifier Figure 2. is a block diagram of a rail-to-rail output amplifier. The output current of the input box gm is sent through a current coupler, which divides the current into two parts and supplies them to the output transistor. The frequency response is determined by two Cc/2s, which are actually connected in parallel. Figure 2. Block Diagram of a Rail-to-Rail Output Amplifier Figure 3. shows the frequency response of the ideal amplifier. Although the electrical principles of the two circuits are different, the behavior is similar. The single pole compensation formed by gm and Cc provides a unity gain bandwidth product frequency of GBF = gm/(2πCc). In the vicinity of GBF/Avol, the phase lag of these amplifiers changes from -180° to -270°, where Avol is the open-loop DC gain of the amplifier. When the frequency is much higher than this low frequency, the phase stays at –270°. This is the well-known "dominant pole compensation", where the Cc dominates the frequency response, hiding the various frequency limitations of the active circuit. Figure 3. Frequency Response of the Ideal Amplifier   Ⅱ Example: LTC6268 Amplifier Figure 4. shows the open-loop gain and phase response of the LTC6268 amplifier with frequency. The LTC6268 is a small and low-noise 500MHz amplifier with rail-to-rail output and only 3fA bias current. It can be used as a good example to illustrate the performance of real amplifiers. The -90° phase lag of the dominant pole compensation starts from about 0.1MHz, reaches -270° around 8MHz, and moves down by more than -270° when it exceeds 30MHz. In fact, all amplifiers have high frequency phase lag, except for the basic dominant compensation lag caused by the additional gain stage and output stage. Generally, the starting point of the additional phase lag is around GBF/10. Figure 4. Open-Loop Gain and Phase Response of the LTC6268 Amplifier with Frequency The stability of the feedback is a matter of loop gain and phase, or Avol multiplied by the feedback coefficient, which is the loop gain. If we connect the LTC6268 in a unity gain configuration, 100% of the output voltage is fed back. At very low frequencies, the output is the negative value of the "–" input, or the phase lags by -180°. Compensation adds a -90° hysteresis through the amplifier, introducing a –270° hysteresis from the "–" input to the output. When the loop phase lag increases to ±360° or its multiples, oscillation will occur, and the loop gain is at least 1V/V or 0dB. The phase margin is a measure of how much the phase lag differs from 360° when the gain is 1V/V or 0dB. Figure 4. shows that the phase margin is about 70° (10pF red curve) at 130MHz, and the phase margin as low as about 35° is feasible.A topic that is not often mentioned is gain margin, although it is an equally important parameter. When it is reduced to zero at some higher frequencies, the amplifier will oscillate if the gain is at least 1V/V or 0dB. As shown in Figure 4, when the phase drops to 0° (or a multiple of 360°, or –180° as shown in the figure), the gain is about –24dB around 1GHz. This is a very low gain and no oscillations will occur at this frequency. In fact, people want the gain margin to be at least 4dB.   Ⅲ Decompensated Amplifiers Although the LTC6268 is fairly stable at unity gain, there are still unstable op amps. By designing the amplifier compensation to be stable only at higher closed-loop gains, the design trade-off can provide a higher conversion rate, wider GBF, and lower input noise than the unity gain compensation scheme. Figure 5. shows the open loop gain and phase of the LTC6230-10. The amplifier is intended to be used with a feedback gain of 10 or greater, so the feedback network will attenuate the output by at least 10 times. Through this feedback network, you can find the frequency when the open-loop gain is 10V/V or 20dB, and find that the phase margin is 58° at 50MHz (±5V power supply). At unity gain, the phase margin is only about 0°, so the amplifier oscillates. Figure 5. LT6230-10 Gain and Phase Change with Frequency It is observed that when the closed-loop gain is higher than the minimum stable gain, all amplifiers will be more stable. Even a gain of 1.5 will make a unity gain stable amplifier much more stable.   Ⅳ Feedback Network The feedback network itself may also cause oscillations. In Figure 6, put a parasitic capacitor in parallel with the feedback divider resistor. It is inevitable that each terminal of each component on the circuit board has a capacitance of about 0.5pF to the ground, and there is also a wiring capacitance. Figure 6. Parasitic Capacitance In fact, the minimum capacitance of the node is 2pF, and there is about 2pF of wiring capacitance per inch of trace. The accumulated parasitic capacitance can easily reach 5pF. Using LTC6268, in order to reduce the power, we set the values of Rf and Rg to a very high 10kΩ. When Cpar = 4pF, the feedback network has a pole at 1/(2π*Rf||Rg*Cpar) or 8MHz. The phase lag of the feedback network is -atan(f/8MHz), we can estimate that the loop will have a phase lag of 360° around 35MHz. At this time, the phase lag of the amplifier is -261°, and the feedback network lags about -79°. At this phase and frequency, the amplifier still has a gain of 22dB, and the gain of the voltage divider is .At the 0° phase, the amplifier's 22dB multiplied by the feedback divider's –19dB produces a +3dB loop gain, and the circuit oscillates. In order to operate normally in the presence of parasitic capacitance, we must reduce the value of the feedback resistor so that the feedback pole can far exceed the unity gain frequency of the loop. That is, the ratio of the pole to the GBF should be at least 6 times.The input end of the op amp itself may also have a considerable capacitance, the same as Cpar. In particular, low noise and low Vos amplifiers have large input transistors and may have larger input capacitance than other types of amplifiers, and the input capacitance is loaded on the amplifier's feedback network. We need to consult the data sheet to understand how much capacitance will be connected in parallel with Cpar. Fortunately, the LT6268 has only 0.45pF capacitance, which is already very low for such a low noise amplifier. The macro model running on LTspice® provided free of charge by ADI can be used to simulate a circuit with parasitic capacitance. Figure 7. shows how to improve the capacitor tolerance of the voltage divider. Figure 7(a) shows a non-negative output amplifier configuration with Rin. Assuming that Vin is a low impedance source (<Rin), Rin will effectively attenuate the feedback signal without changing the closed-loop gain. And it will also reduce the impedance of the voltage divider and increase the feedback pole frequency, which is expected to far exceed GBF. In addition, Rin reduces the bandwidth around the loop and amplifies the input offset and noise.Figure 7(b) shows a negative output configuration. Rg still performs loop attenuation without changing the closed loop gain. In this case, the input impedance is not affected by Rg, but the noise, offset and bandwidth parameters will deteriorate.Figure 7(c) shows the preferred method of compensating Cpar in a non-inverting amplifier. If we set Cf* Rf = Cpar * Rg, then we have a "compensation attenuator", so that the feedback divider now has the same attenuation at all frequencies and solves the Cpar problem. The mismatch in the product will cause "bumps" in the passband of the amplifier and "shelf" in the response curve (At this time, the low-frequency response is flat, but becomes straight near f = 1/2 * Cpar * Rg.).Figure 7(d) shows the equivalent Cpar compensation for the negative output amplifier. The frequency response must be analyzed to find a correct Cf, and the bandwidth of the amplifier is part of the analysis.Here are some comments on current feedback amplifiers (CFA) in turn. If the amplifier in Figure 7(a) is a CFA, then "Rin" has little effect on changing the frequency response, because the negative input is very low impedance and actively copies the positive input. The noise index will degrade slightly, and the additional negative input bias current will actually appear in the form of Vos/Rin. Similarly, in terms of frequency response, the circuit in Figure (b) is not changed by "Rg". The inverting input is not just a virtual ground, it is a real ground with low impedance, and Cpar has been tolerated (only in negative output mode). The DC error is similar to the situation shown in (a), (c) and (d) may be the preferred solution for voltage input op amps, but CFA can't tolerate a direct feedback capacitor without oscillation at all.   Ⅴ Load Problem Just as the feedback capacitor can damage the phase margin, the load capacitor can do the same. Figure 8 shows the change in LTC6268 output impedance with frequency in the case of several gain settings. Note that the unity gain output impedance is lower than the output impedance at higher gains. Full feedback enables the open-loop gain to reduce the inherent output impedance of the amplifier. Therefore, in Figure 8, the output impedance at a gain of 10 is generally 10 times the output impedance at unity gain. Since the feedback attenuator reduces the loop gain, the gain around the loop is 1/10, otherwise it will reduce the closed-loop output impedance. The open-loop output impedance is about 30, which is obvious in the high-frequency flat region of the curve with a gain of 100. In this area, from around gain bandwidth frequency (about 100) to gain bandwidth frequency, there is not enough loop gain to reduce the open loop output impedance. Figure 8. Impedance and Frequency of LTC6268 Under Three Gain Conditions The capacitor load will cause the phase lag and amplitude attenuation of the open-loop output impedance. For example, a 50pF load and our LTC6268 output impedance form another pole at 106MHz, where the output has a –45° phase lag and –3dB attenuation. At this frequency, the amplifier has a phase of -295° and a gain of 10dB. Assuming unity gain feedback is used, we have not fully realized the oscillation because the phase is not brought to ±360° (at 106MHz). However, at 150MHz, the amplifier has 305° phase lag and 5dB gain. The phase of the output pole is –atan(150MHz/106MHz) = -55°, and the gain is .Multiplying the gain cyclically, we get a 360° phase and +0.2dB gain, which is another oscillator. 50pF seems to be the minimum load capacitance that will force the LTC6268 to oscillate.The most common way to prevent oscillations caused by the load capacitor is to simply connect a small resistor in series to the capacitor after the feedback connection. The resistance value of 10Ω to 50Ω will limit the phase lag that may be caused by the capacitive load and isolate the amplifier and low capacitive impedance when the speed is very high. Disadvantages include DC and low frequency errors that vary with load resistance characteristics, capacitive load frequency response is limited, and signal distortion caused if the load capacitance is not constant when the voltage changes.Increasing the closed-loop gain of the amplifier can often prevent the oscillation caused by the load capacitance. Operating the amplifier with a higher closed-loop gain means that at frequencies where the loop phase is ±360°, the feedback attenuator also attenuates the loop gain. For example, if we use the LTC6268, its closed-loop gain is +10, then we will see that the amplifier has a gain of 10V/V or 20dB at 40MHz and a phase lag of 285°. To ignite the oscillation, an output pole is required, causing an additional 75° hysteresis. By -75° =-atan(40MHz/Fpole) →Fpole =10.6MHz, we can find the output pole. This pole frequency comes from a load capacitance of 500pF and an output impedance of 30Ω. The output pole gain is .When the unloaded open-loop gain is 10, the loop gain at the oscillation frequency point is 0.26, so there is no oscillation this time, at least no oscillation caused by the simple output pole. In this way, we increased the tolerable load capacitance from 50pF to 500pF by increasing the closed-loop gain.In addition, unterminated transmission lines are also very bad loads because they will cause "runaway" impedance and phase changes that repeat with frequency (See the impedance of an unterminated 9-foot cable in Figure 9).If your amplifier can safely drive the cable under certain low-frequency resonance conditions, it is likely to oscillate at a higher frequency because its own phase margin is reduced. If the cable must be unterminated, a "back-match" resistor in series with the output can isolate the cable's extreme impedance changes. In addition, even if the transient reflection from the this end of the cable just recoils back to the amplifier, if the resistance of the backward matching resistor matches the characteristic impedance of the cable, the resistor can properly absorb this energy. If the backward resistor does not match the cable impedance, some energy will be reflected from the amplifier and terminals, and back to the unterminated end. When the energy reaches this end, it is quickly reflected back to the amplifier. As a result, there is a series of pulses bouncing back and forth, but attenuate each time. Figure 9. Impedance and Phase of the Unterminated Coaxial Cable Figure 9 shows a more complete output impedance model. The ROUT is the same as what we discussed in the LTC6268, and it is also 30Ω, in addition, add the Lout item. This is a combination of physical inductance and electronic equivalent inductance. The physical package, bonding wire, and external inductance add up to 5nH to 15nH. The smaller the package, the smaller the total value. Figure 10. Inductive Component of Amplifier Output Impedance In addition, any amplifier has an electrical inductance of 20nH to 70nH, especially bipolar devices. The finite Ft of the device turns the parasitic base resistance of the output transistor into an inductance. The harm is that Lout and CL may interact to form a series resonant circuit, then the same problem comes again. If there is no greater phase lag in the loop, the impedance of the series resonant circuit may drop to a level that Rout cannot drive. This may cause oscillations. For example, set Lout = 60nH and CL = 50pF. Resonant frequency is .Just within the passband of the LTC6268. In fact, this series resonant circuit is loaded to the output terminal during resonance, which changes the phase of the loop greatly near the resonant frequency. Unfortunately, Lout is not mentioned in the amplifier's data sheet, but its effect can sometimes be seen on the open-loop output impedance circuit. In short, for amplifiers with a bandwidth of less than 50MHz, this effect is not important.One solution is shown in Figure 10. Rsnub and Csnub form a so-called "shock absorber" whose purpose is to reduce the Q value of the resonant circuit so that the resonant circuit does not have a very low resonant impedance to the output of the amplifier. The value of Rsnub is usually estimated as the reactance of CL to reduce the Q value of the output resonance circuit to about 1. Adjust the size of Csnub to fully insert Rsnub into the output resonance frequency, that is, the reactance of Csnub <Cl. Csnub = 10 * CL is practical. Csnub unloads the amplifier at intermediate and low frequencies, especially at DC. If it is very large, Rsnub will put a heavy load on the amplifier at intermediate frequency, which will affect the low frequency, gain accuracy, closed-loop bandwidth and distortion. However, after a little fine-tuning, shock absorbers are often useful for controlling reactive loads, but shock absorbers must be adjusted through experiments. Figure 11: Using an Output Shock Absorber The negative input of the current feedback amplifier is actually a buffer output and will also have the series characteristics shown in Figure 8. Therefore, it may oscillate under the action of Cpar, just like the output terminal. You should try to reduce Cpar and any related inductance. Unfortunately, the damper on the negative input terminal modifies the relationship between closed-loop gain and frequency, so it is not very useful.   Ⅵ Strange Impedance Many amplifiers have an abnormal input impedance at high frequencies. This is most true for amplifiers with two input transistors in series, such as the Darlington configuration. Many amplifiers have PNP/NPN transistor pairs at the input, and their behavior changes with frequency similar to the Darlington configuration. The real part of the input impedance will become negative at some frequencies (generally much higher than GBF). Inductive source impedance will resonate with the input and circuit board capacitance, and negative real components may provoke oscillations. When driving with unterminated cables, this can also cause oscillations at many repetition frequencies. If it is inevitable to use a long inductive wire at the input, you can disconnect the wire with several series-connected resistors that can absorb energy, or install a medium-impedance shock absorber (about 300Ω) on the input lead of the amplifier.   Ⅶ Power The last source of oscillation to consider is power supply bypass. Figure 10 shows part of the output circuit. LVS+ and LVS– are the unavoidable packaging, IC bond wires, the physical length of the bypass capacitor (inductive like any conductor), and the series inductance of the circuit board traces. It also includes the external inductance that connects the local bypass component to the rest of the power bus (if not the power plane). Although 3nH to 10nH may seem small, at 200MHz, it is 3.8 to 12Ω. If the output transistor conducts a large high-frequency output current, there will be a voltage drop across the power inductor. Figure 12. Power Supply Bypass Capacitor Details The rest of the amplifier needs a noise-free power supply, because these parts cannot suppress power supply noise as the frequency changes. In Figure 13 we can see the power supply rejection ratio (PSRR) of the LTC6268 with frequency. In all operational amplifiers, because there is no ground pin, the compensation capacitor is connected to the power supply, which will couple power supply noise into the amplifier, and gm must cancel this noise. Due to the compensation, PSRR decreases with 1/f, in addition, the power supply rejection actually increases after 130MHz. Figure 13. LTC6268 Power Supply Rejection with Frequency Variation At 200MHz, due to the increase of PSRR, the output current may interfere with the power supply voltage inside the LVs inductor. Through the amplification of PSRR, the interference becomes a strong amplifier signal, driving the output current, generating internal power signals, etc., causing the amplifier to oscillate. This is why the power supplies of all amplifiers must be carefully bypassed with traces and components with very small inductance. In addition, the power supply bypass capacitor must be much larger than any load capacitor.If consider the frequency around 500MHz, then the range 3nH to 10nH becomes 9.4Ω to 31.4Ω. This is enough for the output transistor to generate self-oscillation by its inductance and IC component capacitance, especially when the output current is large (transistor gm and bandwidth increase). Because the bandwidth of transistors is very large, special attention needs to be paid, especially at high output currents.   Ⅷ Conclusion In short, the designer needs to consider the parasitic capacitance and inductance associated with each op amp terminal and the natural characteristics of the load. Usually the designed amplifier is very stable in the nominal environment, but each application needs to analyze it by itself.   Ⅸ FAQ 1. Does your op amp oscillate?Well, it shouldn't. We analog designers take great pains to make our amplifiers stable when we design them, but there are many situations that cause them to oscillate in the real world. ... Improperly designed feedback networks can cause instability. Insufficient supply bypassing can offend. 2. What is oscillator in op amp?An oscillator is an electronic circuit that produces a periodic signal. ... The feedback network takes a part of the output of amplifier as an input to it and produces a voltage signal. This voltage signal is applied as an input to the amplifier. 3. What causes an amplifier to oscillate?Causes of parasitic oscillationParasitic oscillation in an amplifier stage occurs when part of the output energy is coupled into the input, with the correct phase and amplitude to provide positive feedback at some frequency. ... Similarly, impedance in the power supply can couple input to output and cause oscillation. 4. How do you compensate an op amp?Another effective compensation technique is the miller compensation technique and it is an in-loop compensation technique where a simple capacitor is used with or without load isolation resistor (Nulling resistor). That means a capacitor is connected in the feedback loop to compensate the op-amp frequency response. 5. How can an op amp improve stability?To ensure stability, the value of RX should be such that the added zero (fZ) is at least a decade below the closed loop bandwidth of the op amp circuit. With the addition of RX,circuit performance will not suffer the increased output noise of the first method, but the output impedance as seen by the load will increase. 6. What are the requirements of oscillations in an amplifier?Oscillations around the 3dB bandwidth of the amplifier are usually due to input/output feedback. Higher frequency oscillations may only be visible on a spectrum analyzer. They may cause waveform distortion and be affected by touching the amplifier on power and signal cables. 7. How do you stop an oscillating op amp?If the op-amp still oscillates, try these things, in this order:1) Add a small resistor to the op-amp's output, either inside or outside the feedback loop. ...2) Do the same as in the previous step, except use a ferrite bead or chip ferrite instead of the resistor. ...3) Raise the amp's gain a bit. 8. How do you increase the gain margin of an op amp?You can increase the phase margin by making a dominant pole nearer to the zero frequency origin. This is accomplished by compensating the op amp through adding a shunting capacitor in the highest impedance node of the amplifier. This is a very well known technique which is used commonly to increase the phase margin. 9. Why the gain of op amp deteriorate with frequency?All opamps have a limit on upper frequency. In a LPF, at low frequencies, the output amplitude is equal to input. But as the frequency increases, the capacitive reactance decreases and the output amplitude starts to decrease. 10. What is used to avoid or minimize instability in amplifiers?It is often desirable to use capacitance to ground from an amplifier's active input terminals to reduce high-frequency interference, RFI and EMI. This filter capacitor has a similar effect on op amp dynamics as increased stray capacitance. 11. Why op amps oscillate an intuitive look at two frequent causes?With delay in the loop, the amplifier does not immediately detect its progress toward the final value. ... It overreacts by racing too quickly toward the proper output voltage. Note the faster initial ramp rate with delayed feedback. 12. How does an op-amp oscillator work?The Op-amp Multivibrator is an astable oscillator circuit that generates a rectangular output waveform using an RC timing network connected to the inverting input of the operational amplifier and a voltage divider network connected to the other non-inverting input.

Ⅰ IntroductionThe usage of modular electrical connectors has contributed to the global growth of communication and data services. The RJ45 connector is one of the most extensively used varieties in the modular family of devices. AT&T created the modular connector system in the 1960s and 1970s to replace large phone connectors  and their labor-intensive installation. This novel connector system provided a simple, quick, and convenient setup  that could be adjusted on-site by a specialist or installed at home by the user. Over the years, the line has evolved to include data communication stalwarts like as the RJ45, which was designed for computer networking. In fact, RJ45 connectors are often known as Ethernet connectors. CatalogⅠ IntroductionⅡ What is an RJ45 Connector?Ⅲ Types of RJ45 ConnectorsⅣ Applications of RJ45 Connectors Ⅴ Cat5 VS Cat6 CablingⅥ Wiring Pinouts of RJ45 ConnectorsⅦ RJ45 VS EthernetⅧ Things to Consider When Choosing an RJ45 ConnectorⅨ Frequently Asked Questions About RJ45 Connectors Ⅱ What is an RJ45 Connector?RJ45, modular plug, 8P8C, end, connection... they are all interchangeable words. All of these terms refer to the portion attached to the end of an Ethernet cable that plugs into your TV, computer, router, and so on. An RJ45 connector is a ubiquitous modular connecting device that, when paired with a cable, provides data communication service to a variety of electronic devices and systems. The FCC classified the numerous connectors produced using this technique into the Registered Jack (RJ) system in 1976, giving rise  to the RJ label. This was done to verify that phone company hardware and consumer equipment were compatible. The RJ system specifies the physical connector, wiring layouts, and signal characteristics. Metal contacts are separated by insulating plastic channels in RJ45 devices, as in all modular connectors. The channels slide into a matching socket, and the connections lock in place with a tab, making them both secure and detachable. RJ45 devices have 8 pins and 8 wire locations used to handle signals or power, allowing them to accept 4 twisted wire pairs. This RJ45 connector's 8-pin layout is identical to that of 8P8C connections, however true RJ45 connectors also feature a tab that only allows the device to be inserted in one orientation with a corresponding socket to avoid an incorrect wiring connection. As a result, an RJ45 connector is one type of 8P8C connector. However, most 8P8C connectors are commonly referred to as RJ45, which is not entirely correct. 8P8C connectors can be plugged into RJ45 sockets, but not the other way around. Ⅲ Types of RJ45 Connectorsthis video shows 3 types of RJ45 connectors Depending on the application, different types of RJ45 connections are available. These are some examples:1)Standard - 8 position, 8 connector, unshielded.2)Ruggedized - consists of several external elements that protect the gadget from hard situations. Also known as Hi-Rel, which stands for high-reliability.3)Shielded-internally shielded connections with a link to shielded cables. RJ48 is another name for RJ45.4)Miniaturized - RJ45 with a smaller footprint than conventional RJ45.5)10 Pin RJ45 - A 10 pin connector that is utilized when all serial lines are required, such as with a T1 line. Ⅳ Applications of RJ45 Connectors RJ45 connectors are primarily used to connect an internet-enabled device (such as a PC) to another network device such as a server, router, modem, smart TV.  gaming console, and other Ethernet  -enabled devices. Ethernet networks are widely used in both professional and home settings. Hardwiring with RJ45 devices offers faster data transfer while maintaining stability and security, making them appealing for usage in industry and on the factory floor. Ruggedized RJ45 technology is also being used more frequently in data transmission applications that expose system components to moisture, dust, vibration, chemicals, or mechanical stress. Various connector features, such as boots and strain reliefs, enable for the performance required to survive in these situations. When designing Ethernet capabilities into a system, the usual solution for connectivity in networks, peripherals, and telecommunications is to use RJ45 connectors with Cat5 or Cat6 cabling. The expansion of features and capabilities to the RJ45 product range, such as greater speed and ruggedness, has also made this connector method useful for usage outside than office or home networking. The advent of the EtherCAT protocol has resulted in increased use on the production floor and elsewhere. Some of the more recent applications that make use of RJ45 technology are:1)Automation in the Factory 2)Industrial Robotics (manufacturing and assembly) 3)Industrial Process Control4)Quality Assurance Systems5)Network Devices for the Internet of Things(IOT)6)Testing and Measuring Systems7)Systems and Devices for Voice Over Internet Protocol(VOIP) Ⅴ Cat5 VS Cat6 CablingThere are several variants of Ethernet and EtherCAT wiring available. Both Cat5 and Cat6 cables are used to connect computers in a network, but their performance is vastly different. Cat5 cable is constructed of four twisted pairs of wire and, while formerly commonly used, is becoming obsolete owing to the Cat5e cable. Cat5e, which is likewise constructed of four twisted pairs of wire, is up to ten times quicker than Cat5 and has improved resilience to crosstalk or interference due to design improvements. Cat6 is likewise composed of four twisted pairs, but it is quicker than Cat5e, has more bandwidth capacity and functionality, eliminates crosstalk or interference by shielding, and is backwards compatible with Cat5 and Cat5e. Cat6 cable is commonly used in network setups capable of reaching Gigabit speeds. The newer Cat6a cable has thicker plastic housing to decrease crosstalk even further and can be utilized for longer cable runs (up to 328 feet). Cat7 cable gradually increases bandwidth. Cable TypeMaximum BandwidthMaximum SpeedCat 5100 MHz100 MbpsCat 5e100 MHz1,000 MbpsCat 6250 MHz1,000 MbpsCat 6a500 MHz10,000 MbpsCat 7600 MHz10,000 MbpsCat 7a1,000 MHz10,000 Mbps Remember that each of these cable designs uses four twisted pairs, or eight wires, necessitating the use of RJ45 connectors with eight pins to link all of those wires. The identical RJ45 connectors are used by all Cat5, Cat5e, Cat6, Cat6a, Cat7, and Cat7a cables. Ⅵ Wiring Pinouts of RJ45 ConnectorsThe T568A and T568B standards outline the layout of the individual eight wires required for adding connectors to a cable. Both adhere to a standard of covering individual wires in one of five colors (brown, green, orange, blue, or white) with various stripe and solid combinations. When building your own wires, it is critical to adhere to either the T568A or T568B conventions to ensure electrical compatibility with other devices. If you don't make your own cables, you merely need to ensure that the standard is compatible with your equipment. T568B is the more common standard due to historical reasons, however T568A is used in some residences. The color coding of the wires in the connectors is summarized in the table below. PinT568AT568B1white with green stripewhite with orange stripe2greenorange3white with orange stripewhite with green stripe4blueblue5white with blue stripewhite with blue stripe6orangegreen7white with brown stripewhite with brown stripe8brownbrown Several different types of connections are similar to RJ45 and can be readily confused with one another. RJ11 connectors, for example, are slightly narrower than RJ45 connectors because they use six-position connectors rather than eight-position connectors. Aside from that, they appear to be identical. Ⅶ RJ45 VS EthernetEthernet is basically a method of linking computers and other devices that are located in the same physical space. It allows data to be transmitted via a Local Area Network (LAN) or a Wide Area Network(WAN) and links them through cable, letting them to communicate with one another. The Ethernet standard (IEEE 802.3) was developed in the 1980s by the Institute of Electrical and Electronic Engineers(IEEE) and is now the most widely used LAN technology globally. It specifies the criteria for constructing an Ethernet network (connections), the number of conductors needed for a connection, the expected performance, and a data transmission framework. Ethernet technology's widespread appeal can be attributed to the balance it provides between ease of installation, speed, cost, and extensive network protocol support. RJ45 connectors are the most common devices used in network configuration. Ⅷ Things to Consider When Choosing an RJ45 ConnectorThere are a plethora of RJ45 Connectors available on the market. Here are the precise elements to consider when purchasing an RJ45 Connector to assist you choose the ones that best suit your needs.1)Will shielded connectors be required for the system?2)How long will the cables have to be?3)Will the product or system be subjected to high EMI or ESD levels?4)Will we be using integrated magnetics or board-mounted modules?5)Do we need robust or high-reliability devices?6)Which pinout protocol is most suited to the design?7)Will the device or system support Power over Ethernet (PoE)?8)How much bandwidth is required?9)How fast must data be transferred? Ⅸ Frequently Asked Questions About RJ45 Connectors1.What is the difference between RJ11 and RJ45 connectors?RJ45 connectors are typically used to connect to Cat5 and Cat6 cables, whereas RJ11 connects to a telephone cable. RJ45 connectors can connect to a variety of devices in a copper cable network, including switches, cables, computers, routers, and so on. Switches with RJ11 connectors typically include two sockets for a two-line phone system. 2.Is RJ45 same as CAT6?RJ45 is a connector, and CAT6 is a cable, both of which are used in Ethernet networks. RJ45 has eight pins, four of which are visible colors while the other four are striped, four of which are exclusively used for Ethernet. CAT6 has six pins of various colors that link Ethernet networking. 3.How do I identify my RJ45 connector?Examine an RJ45 connector on a cable while holding the flat underside toward you. Pin 1 is on the left. In TIA-568B configuration, the straight through configuration is what you're likely to see for Ethernet use: Striped orange. 4.How do I choose a RJ45 connector?When purchasing cable and connectors from several sources, aim towards the center! For example, if your Ethernet cable has a stated insulated conductor diameter of 1.00mm, choose an RJ45 plug with a 0.95 to 1.05mm insulated conductor range. 5.What are the three types of commonly used RJ45 cabling?Coaxial, twisted pair, and fiber-optic cabling are the three most popular cable types used for Ethernet cabling. 6.Can I use an RJ45 for phone?If you have a two-line phone, you can connect it to a T568A wired jack and both lines will function. The smaller RJ11/12 connectors can be inserted straight into an RJ45 jack. It's not ideal because you risk damaging the other pins, but it's designed to function that way. 7.Can I connect RJ11 to RJ45?Caution: Do not connect an RJ11 plug to an RJ45 socket.RJ11 plugs have the potential to irreversibly damage your RJ45 socket. RJ45 connections are commonly used in data cabling systems. An RJ11 to RJ45 converter is the proper technique to use an RJ11 connector in a data cabling system. 8.Which is better RJ45 or Cat6?Cat5e RJ45 cable offers a lower degree of transmission performance, but Cat6 RJ45 cable has a 250MHz bandwidth, better data throughput, and greater resistance to crosstalk and noise. 9.How does a RJ45 connector work?RJ45 plugs have eight pins that electrically link with the wire strands of a cable. Individual wires are placed into each plug's eight positions, which are spaced roughly 1 mm apart, using special cable crimping equipment. This type of connector is known in the industry as an 8P8C connector, which stands for eight position, eight contact. 10.What is another name for an RJ45 connector?RJ45 is a cable termination specification that specifies physical male and female connectors as well as the pin assignments of wires in telephone lines and other networks that employ RJ45 connections. RJ45 connections are also referred to as data jacks. 11.What is one aspect of the proliferation of communication and data services?Modular electrical connectors. 12.What connector is one of the most widely used varieties in the modular family of devices?RJ45. 13.What was the RJ45 designed for?Computer networking. 14.What are RJ45 connectors often known as?Ethernet connectors. 15.What is an RJ45 connector paired with?A cable. 16.What was the purpose of the RJ label?Verify that phone company hardware and customer equipment worked together. 17.How many pins do RJ45 devices have on the inside to handle signals and power?Eight pins and eight wire locations. 18.What does RJ45 connectors have that only allows the device to be inserted in one orientation with a corresponding socket?Tab. 19.What are most 8P8C connectors referred to as in general usage?RJ45. 20.What can be plugged into RJ45 sockets?8P8C connectors. 

 CatalogIntroductionRelated VideoStructureOperation of USB HubTypes of USB HubWhen Do You Need a USB Hub?Pros and ConsFAQIntroductionA USB hub is a convenient way to add more USB ports to a device. When using USB hubs, all devices must share bandwidth and power supply from the computer's USB port. No matter how many devices are connected, the bandwidth and power from the computer's port remain constant. However, the USB hub has its limitations.  For example, connecting devices that consume too much power can increase their instability, requiring users to read the instructions before using them properly.  When users want to connect to common electronics such as phones, mice and keyboards to power them, the USB hub can meet these basic needs.   Related VideoVideo: What is the difference between a USB hub and a USB charging station?Video Description:In this video, I explain the difference between a USB hub and a USB charging station, and let you know which one you should choose for your needs, depending on whether you are looking to simply charge your USB devices, or also connect them to your PC, Mac, iPhone or iPad. StructureA USB interface can be split into multiple working USB interfaces.It uses a USB HUB controller from the second generation.It is simple to use and can be directly connected to the computer without the need for an external power supply.It is installed as soon as the computer recognizes it, and no driver is required. You can freely plug and play it.It supports USB2.0 at speeds of up to 480Mbps and is backwards compatible with USB1.1.It also includes a current protection device.It is compatible with Windows 95/98/Me/2000/XP, Linux 2.4, and Mac OS 8.5 or later. Operation of USB HubA USB hub has one 'upstream port,' which connects to the host, and several 'downstream ports,' which connect to other hubs or peripheral devices / connections. Most systems operate with hubs that are transparent and do not appear on any system visible mapping. Data received from the upstream port, i.e. the host, is broadcast to all devices connected to the downstream ports, whereas data received from the downstream port is routed only to the upstream port and the host. With the introduction of USB 3, a Point to Point routing capability was introduced, in which a routing string sent in the data packet header allows the host to direct the data to a single destination port. This reduces the amount of data on the USB'network' while also lowering power consumption. Another advantage of using a USB hub is that it can provide a system length increase. For low-speed USB 1.1 devices, for example, USB cables are limited to 3 metres. A hub can be used as an active USB repeater to increase cable length by up to 5 meters at a time. Types of USB HubPowered USB Hub & Unpowered USB HubPowered USB HubPowered or active USB hubs use an external power source to raise the energy level of each hub port to that of an on-system port. Active USB hubs are typically powered by a wall outlet. While active USB hubs are not required to distribute power to all connected devices, the hub does distribute data bandwidth to all connected devices. In brief, the USB ports on your computer generate a small amount of power. When you "split" a port (by plugging in a hub), the power is also split among the additional ports. And, depending on the devices you plug into the hub, there may not be enough power for everything.That is why choosing a powered hub with its own AC adapter is critical. You can fill every port with power-hungry devices without fear of limited amps causing operational problems. Unpowered USB HubUnpowered USB hubs lack an external power source and rely solely on the computer's USB port for power. Unpowered hubs have compatibility issues with devices that require more power than the hub can supply. A USB flash drive, for example, may work perfectly fine when connected to the computer's USB port or an active hub, but it may not power on when connected to a passive hub. The USB 3.0 standard improves on previous versions' power management capabilities and may be able to use higher power devices that hubs running older standards cannot. When Do You Need a USB Hub?Now you might think about some essential factors when you want to purchase a USB hub. Check the connection options first. Users can choose to connect four or five ports.   The second step is to check the cable connection to the main device to determine if the appropriate hub has been purchased.   Third, you should buy a USB device with the latest connection protocol, because older devices have slow transfers or are incompatible.  Finally, you should purchase USB devices that are suitable for the user's daily use situation, including size, portability, etc.   Pros and ConsPowered USB HubPros:Make their own powerCan provide power to high-voltage devicesCan power multiple devices at the same time Cons:Unpowered USB hubs are typically more expensive.Need access to a power outlet. Unpowered USB HubPros:Small and portableless expensive than powered USB hubsThere is no need to look for a power outlet. Cons:High-voltage devices cannot be powered without causing performance issues.Struggle to power multiple devices at the same time. FAQ1.What is a USB hub used for?A USB hub functions as an extension cord for USB devices. It connects to your computer and allows you to connect more devices than your current USB ports allow. Some USB hubs are powered, while others are not. 2.Is it OK to use USB hub?USB hubs are the ideal companion for anyone who has a large number of power-hungry USB devices. A USB hub can meet the needs of any device that requires USB power, from phones to tablets to desk gadgets. It's also convenient because you don't have to look for a spare power plug; simply plug everything into the same hub. 3.Can you plug a USB hub into a wall charger?Yes. You can charge your iPad/iPhone by connecting it to a wall charger with a USB connector, just like any other Apple wall charger. It will work with any other device as long as the power source to which the hub is connected can charge your devices. 4.Can I charge my phone through A USB hub?While non-powered hubs must be plugged into a host system to charge your devices, powered hubs can charge your devices even when those systems are not available. Because they come with their own AC adapter, these USB hubs require access to an electrical outlet or power strip. 5.Can I use USB hub for power?When using power adapters for USB peripherals, the USB ports on the hub are only used for data transfer and do not draw power from the hub. Low-power USB peripherals (such as keyboards and mice) can be used on hubs without a power adapter in conjunction with other low-power USB peripherals. 6.What is the purpose of USB hub?This port hub is remarkably small, but its specs are impressive:1.Connects to your computer via USB 3.02.4 USB 3.0 ports (backwards compatible with USB 2.0 and USB 1.1)3.Data transfer rate up to 5 Gbps4.Supports hot swapping 7.What is 4 port USB hub?The USB splitter expands one usb port to 4 Ports USB3.0 , connects your PC or Laptop with hard drives,USB headphone, speakers, memory cards, mouse, keyboards, USB flash drives, printers ,etc. 8.How to identify USB ports on your computer?Quick Navigation :Method 1. Check Port's Color and LogoMethod 2. Check the USB ControllerMethod 3. Check Pins' NumberUser Comments 9.How to create a programmatically switchable USB hub?1.USB device manufacturing2.USB device validation and development3.Plug/unplug cycle testing4.Functional testing5.Battery charging6.USB device resets7.USB power monitoring8.Controlling USB device enumeration sequence 10.Where is the USB hub port?USB hubs are small devices with a few USB ports that connect to your computer or a power source via a single port. USB hubs expand your capacity for connected USB devices in the same way that a power strip allows multiple appliances to plug in for electricity. 

Executive Summary: What is a Phototransistor?A phototransistor is a light-sensitive semiconductor device that converts incident light into electric current while providing internal gain amplification. Unlike simple photodiodes, phototransistors utilize a bipolar junction structure (NPN or PNP) to amplify the signal, making them highly effective for optical switching, object detection, and encoding systems in modern 2026 electronics.Ⅰ Introduction to PhototransistorsThe phototransistor is a specialized semiconductor device engineered to detect light levels and modulate the current flowing between the emitter and collector based on the photon intensity it receives.While both phototransistors and photodiodes serve as optical sensors, the phototransistor distinguishes itself through high sensitivity attributed to the internal gain of its bipolar transistor architecture. As of 2026, this intrinsic amplification makes phototransistors the preferred choice for applications requiring robust signal detection without complex external amplification circuitry.Ⅱ Video Tutorial: How Phototransistors WorkVisual learners can understand the practical operation of light detection in the following tutorial.Phototransistor Tutorial Phototransistor Video Description:A comprehensive tutorial demonstrating how to utilize phototransistors for precise light detection in circuit design.  Ⅲ What Is a Phototransistor?A phototransistor is an electronic switching and current amplification component that operates by converting photon energy into electrical signals. When light strikes the exposed base-collector junction, a reverse current flows proportional to the luminance intensity.Widely used to convert light pulses into digital electrical signals, these components are powered by light interactions rather than solely electrical bias at the base. They offer high gain and low cost, making them ubiquitous in 2026 consumer electronics. Figure 1: Phototransistor SymbolFunctionally, phototransistors share similarities with photoresistors (LDRs), but with a key distinction: phototransistors generate current and voltage through the photovoltaic effect and amplification, whereas LDRs only change resistance.Transistors with the base terminal exposed are chemically doped to maximize light sensitivity. Photons striking the depletion layer generate electron-hole pairs, activating the transistor just as a base current would in a standard BJT. Silicon-based photosensors typically respond to visible and near-infrared radiation (approx. 400nm to 1100nm). Ⅳ How are Phototransistors Constructed?The phototransistor's structure is specifically optimized for photo-applications by maximizing the area of the base-collector junction. While ordinary bipolar transistors exhibit some photosensitivity, phototransistors feature significantly larger base and collector areas to capture maximum light flux.Figure 2: Construction of a PhototransistorⅤ Semiconductor Material EvolutionHistorical phototransistors utilized a homo-junction structure, fabricated entirely from germanium or silicon. In contrast, modern 2026 phototransistors often employ type III-V semiconductor materials, such as gallium arsenide (GaAs), to target specific wavelengths and increase efficiency.Key structural variations include:NPN Topology: The most popular configuration due to the higher mobility of electrons compared to holes.Heterostructures: Utilizing different materials on either side of the PN junction to enhance conversion efficiency.Mesa Structure: A common physical layout for optimized light absorption.Schottky Junctions: Occasionally used for the collector to improve switching speeds.To ensure optimal sensitivity, the emitter contact is frequently offset, preventing it from blocking light from reaching the active region. Ⅵ How Does a Phototransistor Work?A phototransistor operates by using light to control the flow of current, effectively replacing the base current of a standard transistor with photon energy.Biasing: The collector is biased positively relative to the emitter (in NPN), creating a reverse-biased Base-Collector (B-C) junction.Injection: Light strikes the B-C junction, generating electron-hole pairs.Amplification: The movement of these carriers constitutes a base current, which the transistor amplifies by its gain factor (hFE).Typically, the physical base terminal is left unconnected (floating), as the device is controlled entirely by incident light. Ⅶ Key Electrical CharacteristicsSince phototransistors are essentially Bipolar NPN Transistors with an exposed junction, their V-I characteristics resemble a standard BJT family of curves, but with Light Intensity (mW/cm²) replacing Base Current (IB).Dark Current: When no light is present, a minuscule leakage current flows from collector to emitter. In high-precision applications, minimizing this Dark Current is crucial.Light Current: As light intensity increases, the base current rises, triggering the amplification process. Figure 3: Reverse Bias Configuration The collector current characteristics curve below demonstrates the linear relationship between light intensity and output current in the active region.Figure 4: Collector Current vs. Irradiance Ⅷ Selection Criteria & PropertiesWhen selecting a component for 2026 designs, engineers must evaluate specific properties to ensure the device matches the optical environment.Critical Datasheet Properties:Peak Wavelength: The specific color of light (e.g., 850nm IR vs. 560nm Visible) the device is most sensitive to.Linearity: How accurately the output follows the input light intensity.Sensitivity: The ratio of output current to incident light power.Response Time: The rise and fall time, which determines the maximum data rate (typically slower than photodiodes).Acceptance Angle: The field of view from which the sensor can detect light. Ⅸ Common Types: BJT vs. FETPhototransistors are primarily categorized by their internal transistor architecture:BJT Phototransistor: The standard type. In darkness, it leaks only ~100 nA. Under illumination, it can conduct up to 50mA. This high current handling capability distinguishes it from photodiodes.Photo-FET (Field Effect Transistor): Utilizes light to generate a gate voltage that controls the drain-source current. Photo-FETs offer extremely high input impedance and are more sensitive to weak light signals, though they are less common in general switching applications. Ⅹ Practical Circuit Examples (2026 Applications)The primary goal of phototransistor circuits is to generate a usable output voltage from light-induced current. Unlike photodiodes which often require Transimpedance Amplifiers (TIA), phototransistors have built-in gain, allowing for simpler circuit designs.Common Configurations:Common-Emitter (Inverting): Output voltage drops as light increases.Common-Collector (Non-Inverting): Output voltage rises as light increases.Figure 5: Basic Amplifier Configurations 10.1 Step-by-Step Circuit Implementations 1. Light Operated Relay (Automatic Day Switch)Mechanism: When light strikes phototransistor Q1, it conducts, supplying base current to the driver transistor Q2. Q2 then activates the mechanical relay, turning on the connected load. 2. Darkness Operated Relay (Night Light)Mechanism: By inverting the logic, the relay activates only when light is absent. In darkness, the phototransistor turns off (high resistance), allowing the bias resistor to trigger Q2. 3. Light Interruption Alarm (Security System)Mechanism: This circuit functions as a tripwire. Under normal conditions (laser/light hitting sensor), the phototransistor pulls the SCR gate LOW (off). When the beam is broken by an intruder, the gate voltage rises, latching the SCR and sounding the alarm until manually reset. Ⅺ Datasheet Specifications to WatchTo ensure system reliability, consult the following parameters in manufacturer datasheets:Collector Current (IC): Maximum current the device can handle (typically 1mA - 50mA).Dark Current (ID): Leakage current in total darkness (lower is better for precision).Peak Wavelength (λp): The wavelength of maximum sensitivity.VCE(sat): Collector-Emitter saturation voltage.Rise/Fall Time (tr/tf): Critical for optical data transmission applications.Power Dissipation (Ptot): Thermal limits of the package. ⅻ Pros and Cons AnalysisSelecting the right optical sensor requires balancing sensitivity, speed, and cost.AdvantagesDisadvantagesHigh Gain: Produces higher current output than photodiodes, reducing the need for external amplifiers.Limited Voltage: Cannot withstand high voltages compared to Thyristors or Triacs.Cost-Effective: Inexpensive to manufacture and integrate into ICs.Slower Speed: Slower response time (lower bandwidth) compared to PIN photodiodes.Simplicity: Can drive small relays or logic gates directly in simple circuits.Temperature Sensitivity: Dark current increases significantly with temperature fluctuations. XIII Modern Applications in 2026Due to their versatility, phototransistors are integral to many modern technologies:Optocouplers (Optoisolators): Protecting low-voltage logic circuits from high-voltage spikes in power supplies.Optical Encoders: Used in robotics and motors to detect position and speed.Object Detection: Proximity sensors in smartphones and automated manufacturing lines.Safety Systems: Smoke detectors and light curtain barriers for industrial machinery.Remote Control Receivers: IR detection for consumer electronics (though often integrated with demodulators). XIV Comparison: Photodiode vs. PhototransistorWhile both detect light, their use cases differ based on speed and sensitivity needs.FeaturePhotodiodePhototransistorOutputLow Current (µA)High Current (mA) - AmplifiedResponse SpeedVery Fast (Nanoseconds)Moderate (Microseconds)ApplicationsFiber Optics, High-Speed DataRemote Controls, Light Switches, EncodersNoiseLow NoiseHigher Noise levels XV Frequently Asked Questions1. What type of device is a phototransistor?A phototransistor is a bipolar semiconductor device. It functions as a transistor where the base current is generated by incident photons striking the exposed semiconductor junction, rather than an electrical connection.2. What is the main difference between a standard transistor and a phototransistor?Physically, the primary difference is the packaging. A phototransistor has a transparent lens or window to allow light to reach the junction, and it often lacks an external base pin. Electrically, it is controlled by light intensity rather than input current.3. Is a phototransistor considered a sensor?Yes, it is a discrete photosensor. It detects the presence and intensity of light and converts it into a measurable electrical signal.4. How do you test if a phototransistor is working?You can test it using a multimeter or a simple circuit:Connect the phototransistor in series with a resistor and LED to a power source (checking polarity).Expose the sensor to light; the LED should brighten.Cover the sensor; the LED should dim or turn off.5. Which is better: Photodiode or Phototransistor?Neither is universally "better"; it depends on the application. For high-speed data (like fiber optics), a photodiode is superior. For switching and sensing without extra amplifiers, a phototransistor is more efficient due to its internal gain.{ "@context": "https://schema.org", "@graph": [ { "@type": "Article", "headline": "Phototransistors: The Ultimate 2026 Guide", "datePublished": "2021-12-02", "dateModified": "2026-01-07", "description": "A comprehensive guide to phototransistors, covering construction, working principles, circuit diagrams, and 2026 applications.", "image": "https://www.kynix.com/editor_u/image/20211202/2021120216390176.jpg", "author": { "@type": "Organization", "name": "Kynix Electronics" } }, { "@type": "FAQPage", "mainEntity": [ { "@type": "Question", "name": "What type of device is a phototransistor?", "acceptedAnswer": { "@type": "Answer", "text": "A phototransistor is a bipolar semiconductor device where the base current is generated by incident photons striking the exposed junction." } }, { "@type": "Question", "name": "What is the difference between a transistor and a phototransistor?", "acceptedAnswer": { "@type": "Answer", "text": "The main difference is that a phototransistor has an exposed optical window and is controlled by light intensity, whereas a standard transistor is controlled by electrical current at the base pin." } }, { "@type": "Question", "name": "Is a phototransistor a sensor?", "acceptedAnswer": { "@type": "Answer", "text": "Yes, a phototransistor is a discrete photosensor that converts light intensity into an electrical signal." } }, { "@type": "Question", "name": "Which is better: Photodiode or Phototransistor?", "acceptedAnswer": { "@type": "Answer", "text": "Photodiodes are better for high-speed data applications, while phototransistors are better for switching and sensing applications requiring higher sensitivity and gain." } } ] }, { "@type": "HowTo", "name": "How to Build a Simple Light Interruption Alarm", "step": [ { "@type": "HowToStep", "name": "Setup the Phototransistor", "text": "Connect the phototransistor to a pull-down resistor to create a voltage divider." }, { "@type": "HowToStep", "name": "Connect the SCR", "text": "Connect the output of the phototransistor junction to the Gate of an SCR (Silicon Controlled Rectifier)." }, { "@type": "HowToStep", "name": "Align the Light Source", "text": "Point a laser or light beam directly at the phototransistor. This keeps the SCR gate low (Off)." }, { "@type": "HowToStep", "name": "Trigger the Alarm", "text": "Interrupt the light beam. The phototransistor turns off, voltage spikes at the SCR gate, latching the alarm on." } ] } ]}