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Warm hints: The word in this article is about 3000 words and  reading time is about 15 minutes.   This paper is mainly about how to learn analog circuit design. An analog circuit is a circuit used to transmit, transform, process, amplify, measure, and display analog signals. Analog signals refer to continuously changing electrical signals. Analog circuit is the basis of the electronic circuit, which mainly includes amplifier circuit, signal processing, and processing circuit, oscillation circuit, modulation and demodulation circuit, and power supply.    Analog circuit   Catalogs   I. What’s the Engineering Thinking in Analog Circuit II. Commonly Used Semiconductor Devices III. Negative Feedback Basic Concepts IV. Operational Amplifier Development V. Conclusion FAQ I. What’s the Engineering Thinking in Analog Circuit   Analog circuit is a very important profession, and difficult for people to learn. Now, let me talk about my understanding of the analog circuit. When it comes to the understanding and application of analog circuits, I’ve done some projects and participated in competitions. The analog circuit is an engineering course, and the earning focus is to master the engineering ideas. It’s better to put it into practice, instead of only doing the exams. What is the engineering idea? Encyclopedia +explains as this: "Engineering is the application of science and mathematics. Through this, natural material and energy characteristics can be made into efficient, reliable, and human-friendly products flow through a variety of structures, machines, products, systems, and processes, with the shortest Time, and less refined manpower, so the concept of engineering comes out and it has evolved into an independent discipline and skill. "For example, in analog circuits, there is a very Important engineering thinking - approximation.   In high school physics class, we learn a lot of circuits are ideal circuits. The wire resistance is always 0, the transformer efficiency is 100%, the ideal voltmeter resistance is infinite, the ideal ammeter resistance is 0, and so on. You can see that many times the calculation in an analog circuit will often omit one or two smaller items and use the equal sign instead of the equal sign directly.   Why use an approximation? To put it plainly, people’s understanding of nature in human science is not comprehensive enough to describe the natural phenomenon with absolute precision. Or human’s understanding is limited. By the means of approximation, people have not only achieved an obvious effect on solving the problem but also greatly simplifies the procedure and saves time and effort. With this thought, many achievements have been made in human science, which has also proved its reliability.    Summary Mold itself is a very complex subject, and the molding course is just one of the most basic things. Analog Circuit Meaning is the electronic circuit that processes analog signals. Most of the signals in nature are analog signals, and they have continuous amplitude values, such as the sound signal when speaking. Analog circuits can be such signal processing (of course, need to be converted into electrical signals), such as amplifier to amplify the sound signal, the radio can send analog sound signals, image signals. It can even be assumed that all circuits are based on analog circuits (even for digital circuits, the underlying principle is based on analog circuits). Its importance is self-evident.    Due to the rapid development of digital circuits and programmable devices, many superior features are demonstrated. Many electronic devices are slowly digital but still can not do without analog circuits. The most important analog circuit devices, non-semiconductor devices are none other than. The most basic and commonly used semiconductor devices are diodes, transistors, FETs, and operational amplifiers. II. Commonly Used Semiconductor Devices   The diodes have many roles. Ordinary diodes can be used for rectification, light-emitting diodes can be used for indicator and lighting, regulators can be regulated, varactor diodes can be used for signal modulation. The mold course related to the part of the diode is relatively simple. And many characteristics of the FET are similar to the transistor, so we often explain transistor or amplifier instead.    The basic function of the transistor is to enlarge. The transistor constitutes a variety of circuits because of its features, reflecting a lot of engineering ideas. The transistor-based circuit is the amplifier whose input sound is small, the output sound is great. Amplifier output and the input voltage (or current) ratio is called magnification, also known as gain. For a voltage, if the time for the horizontal axis, voltage vertical axis for mapping, the graph is the voltage waveform. If an amplifier with a gain of 5 inputs a constant voltage of 1V (the waveform on the left is shown below), the output should always be 5V (the waveform is shown in the middle figure below), neither changing with time nor changing with temperature And the input voltage exactly the same shape. However, if the magnification is unstable and constantly changing, the original input signal will be distorted (as shown on the right), and the signal may change from a horizontal straight line to a curved line. This waveform change is called distortion. Voltage waveform   III. Negative Feedback Basic Concepts   The basic concept of negative feedback makes some very powerful people find a good way: negative feedback. What is negative feedback? "Feedback refers to the output of the system is returned to the input and affect the input, thus affecting the overall system output Feedback can be divided into positive feedback and negative feedback is to make the output and input the opposite effect, the system Output tends to be stable. "The above explanation is hard to make sense. I have two examples. When playing the inverted pendulum, we propped up an inverted wooden stick by hand. When the wooden stick was tilted in one direction, we offset the change by moving the hand to the direction of the stick so that the stick could be in our hand's balance.    When I was in high school, I often had a monthly test. I found that some of my classmates had a habit of starting a good study when a test score was poor and going up next time. When the test was better, the next month will be relaxed, so results will come down again, so again and again. Both of these examples illustrate that negative feedback can make the system more stable. We ignore the specific circuit, only draw a simple diagram to illustrate how the transistor amplifier uses the negative feedback. The triangle below shows a transistor consisting of an amplifier, the magnification is A, the input is I, the output O = I * A, because the magnification A instability, so the output waveform will be distorted.  Negative feedback   Some devices have been added to the circuit as follows. The purple circle is the adder, combined with the purple "+", "-" symbol that its output Y = (+ I) + (- X) = I-X, in the actual circuit with the resistance can be achieved; Block F is the feedback device, which means that the signal is taken out from the output O and multiplied by F to get X, so X = O * F, where F <1 (this part can be realized by resistance in the actual circuit). Triangle refers to the amplifier A, mainly composed of transistors, meeting O = A * Y, and A magnification is unstable, easy to be disturbed. Add a feedback device   You can list the equations: Y = I-XO = Y * AX = O * F to calculate the gain of the entire circuit: Formula   If the magnification A is very large, while F is not small, A * F 》》1 symbol "》》" suggests far greater than the approximate idea. The entire circuit magnification: Formula   IV. Operational Amplifier Development   1.Working principle of operational amplifier Because the feedback device can be realized by the resistance, the resistance value of the ordinary resistance is not easily disturbed by the outside world, so the value of F is very steady, so the magnification of the whole circuit is very steady. We succeeded in solving the stability problem of the transistor by negative feedback. We can see here that the feedback part and the amplification part form a ring, so the amplification of the whole circuit is called the loop gain or the closed-loop gain. Before adding the feedback, the amplification of circuit A is called the open-loop gain. Due to the negative feedback, the stability of the circuit is improved, but there is also a cost: Because the AF 》》1, then "A》》1 / F" open-loop gain is much larger than the closed-loop gain, which means the amplifier gain is greatly reduced. But in general, this is worth it for stability. Operational amplifier In the above circuit, in order to actually create a large open-loop amplifier gain A, often with multi-stage transistor amplifier in series design.   Because the high demand for such high-gain amplifiers is very common, so some people in history put them into a finished circuit board module. This is used directly as a component on the line when needed because it’s very convenient. This is the original op-amp, which is referred to as op-amp. The development of integrated circuits makes a large number of transistor components integrated into a small chip possible, so the common integrated operational amplifier turns up today.    The "op-amp" is named for its mathematical operation originally used to simulate computers. Although now widely used digital computer is no longer used to calculate the operational amplifier, but the name still retained. Today, op-amps play an important role in analog circuits and have also become one of the focuses of the analog circuit. The op-amp has virtual short and virtual interrupt characteristics. Usually, op-amp has two inputs U + and U-, an output Uo, between them to meet Uo = A * (U + -U-) op-amp open-loop gain A often up to dozens Million ~ millions, but the op-amp output voltage limited by the supply voltage can not exceed the supply voltage. So the op-amp input-output relationship similar to the shape below. In the figure, the horizontal axis is (U + -U-) and the vertical axis is Uo. Op amp input - output In the middle of a straight line, the op-amp is in the normal state of amplification, called the linear region, meeting Uo = A * (U + -U-). When the absolute value of the input becomes slightly larger, the output will be power limited, no longer satisfying the above relationship. The value of Uo is usually slightly smaller than the supply voltage range (note that the op-amp can be dual supply, that is the supply voltage range can be afloat between a negative value and a positive value), which is called the non-linear region. Rail-to-rail op-amp output can reach the power supply voltage.   When the operational amplifier in the linear region, the Uo value is very limited, but A large. So U + -U- = UoA ≈ 0 or U + ≈ U-. At this time, the positive and negative op-amp input voltage is almost equal, like a short circuit similarly, which is called a short circuit. So only when the operational amplifier in the enlarged area will have "virtual short" characteristics, rather than the inherent properties of the op-amp. On the other hand, due to the internal structure of the op-amp, its input impedance is large.    The input impedance can be simply understood as: the input impedance = input voltage/input current input impedance, which means that the op-amp input with only a small current can work properly. Because of this, an op-amp can be used for some weak current detection, such as the human brain, myoelectric wave, whose maximum voltage is only a few mV, the current value is very small. This feature of the op-amp is called a virtual interrupt, meaning that there is almost no current flowing into the input like the open circuit. Different from the short circuit, a virtual interrupt is the inherent properties of the op-amp, which will not change with the circuit.   2.Op amp non-ideal characteristics   The op amp's non-ideal characteristics of the op-amp by the transistor composition. Obviously, like the transistor, there will be many undesirable characteristics. The actual operational amplifier will not fully meet the short virtual fault characteristics. Its normal work needs input current input, which is called the input bias current.    The same op-amp input offset voltage, input offset voltage, input offset current, and other non-ideal parameters. These non-ideal characteristics, such as the input bias current is small, sometimes will have a great impact on the circuit, resulting in the circuit does not work. Therefore, there are some ways to reduce the impact of these factors. In practical applications, the non-ideal characteristics of the op-amp are a very important issue. There are many ways to eliminate the non-ideal characteristics of the op-amp, but not introduced here.    Other cores of the molding course are the transistor and op-amp. Around these devices, the molding course will explain a variety of circuits, including the calculation of the amplifier circuit analysis, multi-stage amplifier circuit, the amplifier frequency characteristics, the idea of feedback, power amplifier circuit, comparator, oscillator, integrator, differentiator, waveform generation, Signal processing, filter, integrated power supply circuit and so on. When comparing op-amp and transistor In the actual design of the circuit, the op-amp will be more than the transistor. Because many of the features of op-amps are better than triodes, the circuit design is simple, and the cost of op-amps is often not too high.   Many times you can achieve the same effect with the transistor and op-amp and lower cost of each op-amp. Because op-amps integrate a large number of transistors, the average cost per transistor is very low. For example, a conventional audio pre-amplifier can be handled with a universal op-amp. and if you use the transistor, you may need more transistors, and the human cost during design is far higher than the op-amp program. Of course, the transistor has its advantages.    In some very simple circuits, the stability of the magnification is not strictly required, one or two transistors can accomplish. And triodes are often used to save costs. In addition, in some extreme conditions, such as working in high-frequency and high-power environments (such as RF signal transmitting circuits), a well-designed triode circuit will perform much better than an op-amp, or at a much lower cost. Even in some conditions, only the transistors can be completed, then you need to choose the transistor to build the circuit.   This video give a detailed explanation about analog circuit: Analog Circuits Lecture V. Conclusion   Analog circuits are a very complex discipline that involves more than knowledge written in books. Books are generally introduced in accordance with the principle of work, simplifying a lot of difficulties to understand, but in reality, more factors must be considered. So the gap between the actual circuit and the book is very large. Such as triangular wave generator built with an op-amp introduced in analog circuit books usually can not work in all likelihood. However, the main principle of the actual circuit is the same as the book description. Therefore, the design of analog circuits often requires a lot of experience, for there are many things that can not be explained and even difficult to calculate. I hope this article can help you learn more about analog circuits. FAQ   1. What is meant by analog circuit? The Analog electronic circuit includes an analog signal with any continuously changeable signal. While working on an analog signal, an analog circuit alters the signal in some manner. Analog circuit can be used to convert the original signal into some other format such as a digital signal.   2. What is the difference between digital and analog circuits? Analog Circuits and Digital Circuits is a classic way of differentiating between two types of electronic circuits based on the signals they process. To put it in simple words, Analog Circuits deals with continuous analog signals whereas Digital Circuits deals with discrete digital signals.   3. Where are analog circuits used? Analog circuits represent key components of communications and other systems in widespread, growing commercial use. High-speed transistors are essential to the operation of such circuits.   4. Is digital cheaper than analog? If you are looking at the straight-up module cost an analog vs. a digital version, then yes, the analog module will likely be a cheaper solution. However, if you look at the total cost, or the “value” of the digital module versus an analog solution, then digital will in fact be “cheaper”.   5. What is analog design? Analog design is part of integrated circuit design and focuses on signal fidelity, amplification and filtering. Those who perform the function of analog design are qualified electrical engineers.   6. Why is analog design difficult? Ask most engineers and they would tell you why: analog design is harder than digital, and requires more knowledge and more factors to consider such as a deep understanding of efficient power, precision measurement, wireless connectivity, and reliable circuit protection.   7. Which is better analog or digital design? Analog circuits can be precise, elegant design with various components with very simple. For example, two resistors joining to make a voltage divider. Generally, Analog circuits are much more complex to design compared to which complete the same task as digitally.   8. What is the tool used for analog circuit design? A suite of web tools to help you design signal conditioning circuits faster: Analog Filter Wizard, Precision ADC Driver Tool, Photodiode Wizard, In Amp Diamond Plot, Direct Digital Synthesis Simulator, and Virtual Eval.   9. How hard is circuit design? Circuit design is a lot like any other learned skill, you start with the basics. These basic circuits can be learned in a few days. ... So yes, it can be very difficult to reach a high level of design expertise and you never really master it because the art continues to evolve.   10. How does circuit design work? Digital electronic circuit design takes the electrical signals in the form of discrete values. The data are represented in the form of zeros and ones. Digital circuits extensively use transistors, interconnected to give create logic gates that provide the function of Boolean logic.   You May Also Like:   Look Forward to the Future of Semiconductor GaN High-Electron Mobility Transistor Power Amplifier Trojans are everywhere even the hardware Remote Electronic Transport Promote Organic Photovaltaic Power Generation Make Next-Gen of Computer Be Faster,Better, More efficient Some suggestions about protecting transformers  

Warm hints: The word in this article is about 1000 and the  reading time is about 6 minutes.SummaryFujitsu,a company that provide innovative IT services and digital technologies like mobile,AI,cloud or etc,announced the development of a gallium-nitride(GaN) high-electron mobility transistor(HEMT) power amplifier for use in W-band(75-110 GHz)transmissions in July 2017 at the 12th international Conference. To realize long-distance,high-capacity wireless communications,a promising approach is to utilize the W-band and other high frequency bands that encompass a broad range of usable frequencies, and increase output with a transmission power amplifier. At the same time, demand exists for improved efficiency in power amplifiers in order to mitigate the increased power consumption of communication systems. Fujitsu has now succeeded in developing a power amplifier for use in W-band transmissions that offers both high output power and high efficiency, improving transistor performance through the reduction of electrical current leakage and internal GaN-HEMT resistance. Fujitsu has achieved 4.5 watts per millimeter of gate width, the world's highest output density in the W-band, and has confirmed a 26% reduction in energy consumption compared to conventional technology. Fujitsu anticipates that setting this power amplifier between wireless communication systems in two locations will achieve high-bandwidth communications at 10 gigabits per second (Gbit/s) over a distance of 10km. Part of this research was carried out with support from Innovative Science and Technology Initiative for Security, established by the Acquisition, Technology & Logistics Agency (ATLA), Japan Ministry of Defense. Development Background Wireless data traffic from mobile communications has increased dramatically over the last few years, and with the spread of 5G and IoT devices it is predicted to increase at an annual growth rate of 1.5 times until the year 2020. In order to build this sort of high capacity next-generation wireless communications network, attention has been focused on wireless communication technology using the high frequency W-band. The range of frequencies that can be used in the W-band is very broad, and because communication speed can be rapidly increased in this band, it is well-suited for this kind of high bandwidth wireless communication. Conventional wireless communications technology, has allowed for performance of several Gbit/s over distances of several kilometers, but achieving an even greater increase in wireless communication distance and capacity utilizing the W-band demands further increases to the output of power amplifiers to boost signals during transmission. Issues To increase distance and capacity, it will be necessary to expand the frequency bandwidth that can be amplified while simultaneously supporting modulation methods that can transmit more information within the same frequency bandwidth, and a strong requirement is to have less distortion when the signal is amplified. Another pursuit is keeping in check the energy consumption of communication systems that accompanies greater distances and capacities, and the improved energy efficiency in power amplifiers.In order to both increase the distance and capacity of wireless communications and decrease energy consumption with indium-aluminum-gallium-nitride (InAlGaN) HEMTs, Fujitsu has developed two technologies that effectively reduce internal resistance and current leakage. Features of the newly developed technologies are as follows: Technology to reduce internal resistance Fujitsu has developed device technology that can reliably reduce resistance to one tenth that of previous technology when current flows between the source or drain electrodes and the GaN-HEMT device. The technology utilizes a manufacturing process that embeds GaN plugs directly below the source and drain electrodes, which generate electrons at high densities (fig. 1). It is necessary to transport the electrons that come from the source electrode to the two dimensional electron gas field as smoothly as possible. The structure of the previous technology causes the electron supply layer to become a barrier, however, and internal resistance increases between the source electrode and the two dimensional electron gas. By applying this new technology, Fujitsu succeeded in running high currents through the transistor with significantly less resistance (fig. 2). Technology to control current leakageA current leakage occurs when the two dimensional electron gas, which moves at high speed on the boundary at the top of the channel layer, takes a detour below the gate when the transistor is in its off-state. This leakage causes deterioration in the operational performance of the power amplifier. Normally, it is possible to reduce current leakage by placing a barrier layer beneath the channel layer, but in that case the amount of two dimensional electron gas also decreases, and leads to a reduction of the drain current. This new technology maintains high drain currents by effectively distributing indium-gallium-nitride (InGaN) to create a barrier layer below the channel layer. This reduces electron detours during operation, successfully providing significant reductions in current leakage(just see the fist and second picture).Effects The previous world record for power amplifier output density in the W-band for transmitters was 3.6 watts per millimeter of gate width with technology developed by Fujitsu Laboratories. This has improved significantly with the newly developed technology, which delivers power output of 4.5 watts per millimeter of gate width for a power amplifier designed to operate at 94GHz. In addition, this new technology achieved a reduction in energy consumption of 26% compared to the previous technology through a reduction in current leakage. It is anticipated that the use of this power amplifier will allow the achievement of high capacity, long distance wireless communications between two connected systems at different locations at over 10Gbit/s and at distances greater than 10km.Fujitsu aims to apply this technology broadly to the development of power amplifiers for purposes that call for wireless communications that offer long range and higher capacity, while offering easier installation than fiber optics. The goal is to commercialize this technology in high speed wireless communication systems by 2020, with an aim to employ it in such situations as a method of restoring communications when fiber optic cables have been severed by natural disasters or as a way of setting up temporary communications infrastructure when holding events.  Article provide by FujitsuArticle edited by kynix

In this article today, we will introduce 9 simple audio amplifier circuit design schematic diagram with detailed explanation, complemented with some knowledge about amplifier.     Catalog   I. What is an Audio Amplifier? II. Nine Simple Audio Amplifier Circuit Design Schematic Diagrams III. Some Knowledge about Amplifier FAQ     I. What is an Audio Amplifier? Let's watch a video first. This video shows us how to make a great sounding LM386 audio amplifier with bass boost An audio amplifier is a device that reconstructs an input audio signal on an output element that produces sound. The reconstructed signal volume and power level are ideal. They are truthful, effective, and low distortion. The audio range is from 20Hz to 20 kHz, so the amplifier must have a good frequency response within this range. Depending on the application, the power varies greatly. From milliwatts of headphones to several watts of TV or PC audio, to dozens of watts of mini home stereo and car audio, to hundreds of watts or more of more powerful household and commercial audio systems, until the power is big enough to meet the sound requirements of an entire cinema or auditorium.   The development of audio amplifiers has gone through three times. They are electron tube (vacuum tube) time, bipolar transistor time, and field-effect transistor time. The electronic tube audio amplifier has a round and sweet timbre, but it has the disadvantages of large volume, high power consumption, unstable operation, and poor high-frequency response. For the bipolar transistor audio amplifier, it has the advantages of a wide frequency band, large dynamic range, high reliability, long life, and high-frequency response is good. However, its static power consumption and on-resistance are very large, and the efficiency is difficult to improve. The third one is the field-effect transistor audio amplifier. It has the same round and sweet timbre as the electron tube and its dynamic range is wide. More importantly, it has a small on-resistance and can achieve high efficiency. Figure 1 II. Nine Simple Audio Amplifier Circuit Design Schematic Diagrams Next, I would like to introduce nine simple audio amplifier circuit design schematic diagrams.   Circuit Diagram 1 This circuit makes full use of the conventional LM317 voltage adjustment chip,  so that it not only completes the voltage stabilization function of the unstabilized voltage after filtering but also realizes the function of amplifying the audio signal picked up by the electret capacitive microphone. The electret capacitive microphone contains an impedance converter based on JFET, which converts the speech signal into a current form and adds it to the RP resistor, causing the corresponding voltage change. 220V AC output 36V unstable DC through transformer and bridge rectifier, and after filtering by the capacitor, the low resistance audio amplification signal input by the LM317 on the DC is fed into the capacitor and output to the loudspeaker. The implementation circuit is shown in figure 2.   Figure 2 After the circuit is installed, the voltage difference between the two inputs of the electret capacitive microphone should be adjusted first. This voltage difference is required to be less than 1.25VDC. By connecting an adjustable resistor between the LM317 adjustment end and the ground, the required limit can be achieved by adjusting the resistance by Rp. Secondly, the audio signal picked up by the microphone is easy to be interfered with by external noise. The addition of C1 can filter out part of the interference signal, but the required signal is also attenuated. Because the internal gain of the LM317 can compensate for the attenuation part, the loss caused by the introduction of C1 is negligible.    In order to avoid excessive loss, the capacity of C1 should be as low as possible, this circuit takes 15F. Finally, it should be noted that the minimum operating current requirement of the LM317 chip is 4 mA when the circuit is working normally, and a load resistor is used to absorb the 4mA current. If a low impedance loudspeaker is used, this load resistance must also be introduced to compensate for the signal distortion. In a practical circuit, if an 8Q impedance loudspeaker is used, at least 420Q load resistance is used to compensate for the possible signal distortion.   Circuit Diagram 2 Figure 3     Circuit Diagram 3 Adjust R1 so that the signal is not distorted at the maximum output, and reduce R2 to output more power. If there is a multimeter, the collector voltage of the transistor can be adjusted to about half of the power supply voltage. Figure 4     Circuit Diagram 4 In this design, the gain control of the preamplifier adopts DC volume control mode is realized as shown in figure 5. The preamplifier is an inverse proportional amplifier composed of a fully differential operational amplifier and resistor. Its gain is determined by the ratio of feedback resistance to input resistance. The external input DC analog control signal Vc is converted into control data through the gain control module (GainCon-troD), which is used to control the ratio of the feedback resistance of the preamplifier to the input resistance, and then adjust the change of the gain. Figure 5   The operational amplifier adopts a two-cascade structure, as shown in figure 6. In the first stage, a folded common-source common-gate amplifier with PMOS input is used to provide a large gain. At the same time, the common-mode range of the input is increased and the flicker noise is reduced. The load of the folded input tube adopts a current source load with a source feedback structure to increase the output impedance and reduce noise. The second stage uses a common-source amplifier to provide a large swing.    In order to maintain the stability of the closed-loop, Miller compensation capacitance is added. At the same time, in order to counteract the influence of the zero points of the right half-plane, the zero adjusting resistance in series with the compensation capacitor is inserted into the feedforward path of the compensation capacitor. In the design of the common-mode feedback circuit, the common-mode feedback structure with resistance distributor and amplifier is adopted.     Figure 6   Circuit Diagram 5 The audio amplifier uses very few peripheral components and works well at 2v. （The circuit is shown in figure 7）   The TDA7052 is a mono amplifier designed for battery-powered portable tape recorders and radios with an internal gain set at 40dB. Now the recorder and radio tend to be miniaturized and the battery consumption is reduced, which means that the power supply voltage is reduced, and the output power is also reduced. In order to compensate for this loss, TDA7052 uses the bridge drive load (ETL) principle, which can make the output power of 8 EU load up to 1.2 w.   Figure 7 lists the working parameters of TDA7052. Except for special instructions, the power supply is 6 v, the load impedance is 80, the input signal frequency is 1 kHz and the ambient temperature is 25 degrees.   Figure 7   Circuit Diagram 6   TDA2822 Fabrication of microphone Power Amplifier Circuit The circuit has few peripheral components, simple fabrication, but surprisingly good sound quality. A dual audio amplifier integrated circuit is used and its main characteristics are high efficiency and low power consumption. The typical value of static working current is only about 6mA. The integrated circuit has strong voltage adaptability (from1.8V to 15V DC) and will still have a power output of about 100mW even if it is used at a low voltage of 1.8V. The specific circuit is shown in figure 8. Figure 8   The electret microphone MIC converts the picked sound signal into an electrical signal, which is introduced from the foot 2 of U1 by C2 and W, and amplified by U1 audio to promote the loudspeaker pronunciation. The machine is connected with a BTL output circuit, which is good for improving sound quality and reducing distortion. At the same time, the output power is increased fourfold. When a 3v voltage is used, the output power is 350mW.   The resistance R1 and R2 are 1/4W metal film resistance, W is a small carbon film potentiometer and C2 is preferably a monolithic capacitor. If there is no good quality ceramic capacitance, select high quality, voltage resistant, and low leakage current electrolytic capacitor for C1, C4, and C3. Choose high sensitivity electret microphone as MIC, choose small button switch or toggle switch for K and choose TDA2822M or TDA2822 or D2822 for U1. According to the numerical value in figure 7, it can work normally without debugging.     Electret microphone detection For example, the R*100 of MF 47 multimeter is used to measure the Great Wall CZ Ⅲ electret microphone. When the black watch pen is connected to the core line and shell of the electret microphone, the multimeter pointer refers to the value at 3k Ω. When blowing hard, the pointer refers to the value at 4k Ω (and the resistance value of some microphones becomes smaller). If you blowhard and the multimeter pointer wobbles very little, you can adjust the two watch pens and try again. If the multimeter needle is still wobbling very little, the electret microphone is damaged.   In application, the drain D of the electret microphone must be connected to the positive electrode of the power supply through a resistance of 4.7 to 10k Ω, and then connected to the amplifier circuit, as shown in figure 9. Figure 9   Circuit Diagram 7    Add an amplifying circuit to the microphone  The electronic components are as follows：                                                                    resistance R1：1k Ω resistance R2：1m Ω resistance R3：1k Ω transistor vT：9014 capacitance：4.7 UF capacitance C2 ：4.7 UF battery：AA size battery     Figure 10    Working principle of amplifier circuit  Fig. 10 is a circuit diagram of the entire microphone amplifier circuit. As you can see from fig. 10, there are only six or seven originals of the whole circuit. The following is a brief description of how it works, in which the resistor R1 is responsible for providing the operating voltage to the microphone, R2 and R3 are responsible for providing the bias voltage for the transistor, and the capacitor C1 is responsible for coupling the signal of the microphone to the transistor for amplification. Finally, the amplified signal is coupled through capacitance C2 and sent back to the positive pole of the microphone line, that is, the outermost shielding layer of the microphone line (that is, the outer layer of copper mesh). Figure 10 is the material or electronic component we use to make it.    Considerations in production  The specifications of the electronic components required for the whole amplifier circuit are as follows: resistance R1：1K Ω resistance R2 ：1m Ω resistance R3 ： 1K Ω transistor VT ：9014 capacitance C1：4.7 μ F capacitance C2 ：4.7 μ F battery： a general AA size battery. △ Generally speaking, it can be used for about half a year if it is used normally.    Pay attention to the following points in the production process： 1. The pin of the transistor must be connected correctly; otherwise, it will not play the role of amplification. The pin distinguishes the following transistors lead down and the flat side facing itself. The transistors are E (emitter), B (base), and C (collector);   2. The microphone head is also polar. (see figure 4 for a specific distinction);   3. The polarity of the coupling capacitance can be distinguished by marking, and the pin with an arrow and marked "-" is a negative electrode, and the positive electrode is generally not marked   Because the components are few or can be directly welded in the shed, the circuit board can be directly installed into the base of the microphone, and the power lead of the circuit board can be connected to the battery slot reserved by the microphone.     Effect Test After trial, the effective distance of the microphone can reach 5 to 6 meters, and the effect is also obvious with the voice input function of Office Word 2003, and the speech can also be accurately recognized about 1 meter away from the microphone.   Circuit Diagram 8 A transistor is required. First, output the MP3 signal and use a lower power tube to amplify it. Then push medium power tube. This can achieve small distortion and have the coupling undone. This transistor circuit is simple, practical, and also easy to make.     Figure 11 The circuit is powered by a 9V single power supply. The input signal is coupled to the base of 9014 through 47uF capacitance. 9014 is responsible for preamplifier, and works in Class A state. 5.6K and 1.5K resistors are bias resistors of 9014, and 5.6K resistors are negative feedback resistors at the same time. 22 Ω resistors is a current series negative feedback resistor, which is used to increase the input impedance and reduce the linear distortion by 9014. The 470 Ω resistor is a 9014 collector load resistor used to convert the 9014 amplified current into a voltage, and two 1N4148 diodes are used to set the post-stage complementary tube in the pre-conduction region. OTL complementary output circuit is composed of 8050 and 8550. 3.3 Ω resistors are negative feedback resistors in series with emitters, which act the same as 22 Ω resistors. The 1000uf capacitor is the output capacitor, which is used to separate the DC and allow the AC signal to pass through. 8050 and 8550 are used as power output tubes to form a complementary push-pull output circuit, and the amplified current of 9014 is further amplified to push the loudspeaker. The static bias current of the push-pull circuit is set by two 1N4148, and the two 1N4148 are temperature compensation elements of two power output transistors at the same time. The voltage at the positive contact of the 1000uF electrolytic capacitor shall be half of the supply voltage. Because the conduction voltage of the silicon transistor base is 0.7 V, the base voltage of 8050 can be obtained to be about 5.2 V. From this, the static bias current of 9014 is (9- 5.2) / 470 =8 [mA]. The emitter voltage of 9014 is 8*22=0.176 V, and the base voltage is 0.176+0.7≈0.87V. Circuit Diagram 9 As long as R3 is increased, the gain of the amplifier can be increased. The parallel capacitor C4 at both ends of R3 is used to provide low resistance path filtering to high frequency to prevent high frequency self-excitation. J1 is a jumper, when J1 is turned on, foot 1 is grounded and the full power amplifier works; when J1 is disconnected, foot 1 is VDD, micro-power off, and the amplifier does not work. Jumper J2 can also control the operation of the amplifier. When J2 is disconnected, the + IN end is unbiased and the amplifier does not work. But if it is connected,  the amplifier works. LM4819 high gain audio amplifier circuit is shown in figure 12. Figure 12   III. Some Knowledge about Amplifier      Distortion  Also referred to as THD+N, Total Harmonic Distortion + Noise is simply a measure of the effect that an amplifier will have on sound output. The lower the distortion is, the closer your amp’s output will be to the original recording’s sound. The more distortion that there is, the more coloration there will be to the sound. Just keep in mind that your speakers will also have an impact upon sound, so choose them wisely by matching them with the right amplifier for the clearest sound.    Left and Right Signals  Crosstalk is a term that refers to the measure of how much of the right signal is mixed with the left signal. Amps come as a single unit, but they need to send signals out separately to the speakers so that you can hear things like a piano on the right and a singer to the left. If there is a lot of crosstalk, though, it will be much more difficult to decipher where the different sounds are coming from.    Power  When you look at an amp’s specs, you will also notice that there is a number for the power output, which is basically how loud the music can go. For the average listener, a 10W amp would be sufficient, as it will let you play your music loudly without creating any distortion. If you are really looking for a super loud amp, though, you can go as high as 100W. It really depends upon what your preferences are, what you will be using your amp for, what speakers you have, and how much room you have.    Connections  Your amp should have plenty of inputs for anything and everything that you wish to plug into it. You could have a 3.5mm connection for your iPod, and you could have a USB connection for your laptop, as a couple of examples. Just don’t sacrifice sound quality for more inputs.    Signal vs. Noise  There will always be some background noise within your amplifier, just as there is always some background noise in your own environment. What you want is an amp that will ensure the background noise is not obvious or perceptible. This will ensure that you will hear all of the music but none of the noise. Checking the signal to noise ratio on an amp will give you clearer insight into how well the product will work in this area.   FAQ   1. What does an audio amplifier do? An audio power amplifier (or power amp) is an electronic amplifier that amplifies low-power electronic audio signals such as the signal from radio receiver or electric guitar pickup to a level that is high enough for driving loudspeakers or headphones.   2. What is the difference between a speaker and an amplifier? Speakers are those things that make sound. The amplifier is what delivers sound to the speakers. Amps are usually radios and speakers are what you plug into the amp/receiver to hear the sound. ... The speakers plug into the sound card which in this case would loosly be called the amplifier.   3. Does amplifier improve sound quality? An amplifier simply increases(magnifies)the components of sound quality. If the quality of the input sound is poor, it will be a louder poor sound ; meaning you will hear the poorness of the sound more. It amplifies everything, the good and the bad.   4. Why do you need an amplifier? An amplifier is the device that turns the low voltage signals from your source equipment into a signal with enough gain to be used to power a pair of speakers. ... The second does the 'heavy lifting' and adds the gain to the signals in order to be used to power a pair of speakers. This is the power amplifier.   5. Which is better amplifier or receiver? A receiver is definitely the more convenient choice of the two, but that doesn't mean that it comes without any downsides. Usually a Lower Quality Amplifier - Though the quality of receiver amps is definitely increasing, you still don't have a completely dedicated amp with a receiver.   6. Which is more important speaker or amplifier? A speakers performance is highly variable and its sound will depend on the amp driving it. But the greatest amp (whatever that is) will sound like crap if the speaker sounds like crap. The quality of the speaker is the ultimate limitation of your system (assuming proper set up and room integration)   7. Can I hook up 8 ohm speakers to a 4 ohm amplifier? Yes, you can use 8 ohm speakers with a 4 ohm amplifier. Just wire two 8 ohm speakers of the same wattage in parallel.   8. How much money should I spend on an amp? If it's just for practicing in your bedroom, you can get a perfectly adequate little practice amp for under $200. If you'll be playing in a band or gigging out, yeah, you probably should expect to spend in the $500-700 range at least.   9. Do you need an amp for a subwoofer? Subwoofers are designed to increase the bass frequencies, resulting in a deep, thumping sound. In most cases, they are paired with an amplifier to boost the sound. If you do not have the funds for both components, you can still hook up a subwoofer without an amplifier; it simply involves a little more know-how.   10. Which transistor is used in amplifier? In most of the electronic circuits, we use commonly NPN transistor configuration which is known as NPN transistor amplifier circuit. Let us consider a voltage divider biasing circuit which is commonly known as a single stage transistor amplifier circuit.     Reference Component LM3886TF LM4652TA LM4765T  

The LTC2185 is a 125Msps 16-bit ADC with excellent noise and linearity performance while only consuming 185mW per channel. It is ideal for demanding low power applications that require excellent AC performance. A high performance ADC like the LTC2185 requires a high performance amplifier driving it to maintain the excellent performance. The ADA4927-1 delivers the linearity performance required by the LTC2185 while only consuming 215mW. The well designed package of the ADA4927-1 allows for a simple layout that reduces parasitic capacitance in the feedback path that can erode the phase margin of the amplifier. This combination of ADC and driver allows excellent performance from 62.5-125MHz a region where other high speed amplifiers are lacking.  The LTC2185 is a two-channel simultaneous sampling parallel ADC which offers a choice of full-rate CMOS, or double data rate (DDR) CMOS/LVDS digital outputs. Pin-compatible speed grade options include 25Msps, 40Msps, 65Msps, 80Msps and 105Msps with approximate power dissipation of just 1.5mW/Msps per channel. It includes popular features such as the digital output randomizer and alternate bit polarity (ABP) mode that minimize digital feedback when using parallel CMOS outputs.  Analog full power bandwidth of 550MHz and ultralow jitter of 0.07psRMS allows under-sampling of IF frequencies with excellent noise performance. To maintain this level of performance the LTC2185 needs to be driven with an appropriate amplifier like the ADA4927-1. The ADA4927 is a high speed differential current feedback amplifier. Fabricated on Analog Devices’ silicon-germanium process, the ADA4927-1 has excellent distortion and an input voltage noise of only 1.3nV/rtHz. This allows it to drive high speed ADCs like the LTC2185. The gain of the ADA4927-1 is set with external feedback resistors located next to the input pins.  By keeping the feedback pins and input pins close on the package, the ADA4927-1 provides a clean layout and minimizing the parasitic capacitance in the feedback network. This make the ADA4927-1 an ideal choice for driving high performance ADCs, like the LTC2185, from DC to 125 MHz. Figure 1 shows a schematic of the ADA4927-1 driving the LTC2185. The corresponding layout is shown in figure 2.  The feedback pins on the ADA4927-1 are adjacent to the input pins which minimizes the parasitic capacitance of the feedback node and improves the phase margin of the amplifier. It also Simplifier the layout by making it possible to place feedback resistors directly across the two pins and not having additional trace length in the feedback path. There is a simple filter between the amplifier and ADC that reduces the wideband noise of the amplifier and improves the SNR of the system. This filter also attenuates the sampling glitches from the ADC before they reach the amplifier. This helps keep the output network of the ADA4927 from oscillating in response to these glitches. This filter network can be modified to accommodate a wide range of input bandwidth requirements. (Figure 1:  Schematic showing an ADA4927-1 driving one channel of the LTC2185)(Figure 2:  Layout showing an ADA4927-1 driving once channel of the LTC2185)Figure 3 and figure 4 show the SNR and SFDR of the LTC2185 and ADA4927-1 combination. The SFDR stays above 67dB out to 125MHz while the SNR is better than 63dB to the same frequency. This combination only consumes 250mW. With a sample rate of 125Msps, this combination provides good performance through the entire 2nd Nyquist zone where other amplifiers begin to have poor linearity.  (Figure 3:  SNR of the LTC2185 driven with the ADA4927-1)(Figure 4:  SFDR of the LTC2185 driven with the ADA4927-1) Using the ADA4927-1 to drive the LTC2185 provides excellent linearity while keeping the power consumption low. The fact that the ADA4927-1 stays very linear out to 125MHz allows this ADC amplifier combination to be used in demanding communication and medical applications that require the use of the second Nyquist zone of the LTC2185. The pin out of the ADA4927-1 and filter design minimize the complexity of the layout while maintaining excellent performance on a low power budget. Ref.KY32-LTC2185KY362-ADA4927-1 

Researchers at Chalmers University of Technology, Sweden, have demonstrated an integrated amplifier with the lowest noise performance so far. The amplifier offers new possibilities for detecting the faintest electromagnetic radiation, for example from distant galaxies.Last year, Chalmers reported a world record for a low-noise amplifier in the prestigious journal Electron Device Letters. The amplifier exhibited a minimum noise figure of 0.018 dB across a bandwidth of 4-8 GHz. However, since the low-noise amplifier was designed in a hybrid solution, scaling up to larger quantities turned out to be very difficult.Chalmers has now in collaboration with a company called Low-Noise Factory published an article on an integrated ultra-low-noise amplifier. The scientists have developed a unique indium phosphide-based process for what is known as high electron mobility transistors (HEMT). Transistors and other semiconductor components have been fabricated on a monolithic chip on an indium phosphide wafer. All parts of the design such as semiconductor layers, components, process and circuit design have been optimised for the lowest noise performance.As a result, an integrated 2.0 x 0.75 mm amplifier with an ultra-low-noise figure of 0.045 dB was demonstrated. The amplifier had a very large bandwidth of 0.5-13 GHz and a high gain exceeding 38 dB across the frequency band. In order to show such extreme performance, the amplifier was cooled to minus 260 degrees of Celsius."The combination of high gain, large bandwidth and ultra-low-noise figure makes this circuit very attractive for large multipixel arrays containing thousands of antennas," says Jan Grahn, research group leader at Chalmers."The integrated ultra-low-noise process enables the fabrication of thousands of amplifiers with identical performance. One potential future application is in the world's largest radio telescope SKA (Square Kilometer Array) that is being planned, an international project where the Onsala Space Observatory at Chalmers is one of the acting members. In huge applications such as the SKA, even a small noise-figure reduction in the first low-noise amplifier in the receiver chain may potentially bring about major savings in the final system design." 

Fujitsu today announced the development of a gallium-nitride (GaN) high-electron mobility transistor (HEMT) power amplifier for use in W-band (75-110 GHz) transmissions.This can be used in a high-capacity wireless network with coverage over a radius of several kilometers. In areas where fiber-optic cable is difficult to lay, to achieve high-speed wireless communications of several gigabits per second, one promising approach is to use high-frequency bands, such as the W band, which uses a wide frequency band. In order to get good long-distance coverage in these frequencies, however, it is necessary to increase the output power of the power amplifier to the scale of watts. Fujitsu succeeded in developing a power amplifier for W-band transmissions using GaN-HEMT technology capable of high output at 100 GHz. Evaluations of the newly developed power amplifier confirmed it to have 1.8 times increased output performance than before, which would translate to an increase of over 30% in transmission range when used in a high-speed wireless network. A portion of this research was conducted as part of a project of the National Institute of Information and Communications Technology (NICT) on "Agile Deployment Capability of Highly Resilient Optical and Radio Seamless Communication Systems." Details of this technology are being presented at Power Amplifiers for Wireless and Radio Applications (PAWR2016), opening January 24 in Austin, Texas.High-frequency wireless communications, using the frequency band known as the W band (75-110 GHz), are drawing increasing interest, both as a way to temporarily set up high-capacity communications channels for handling special events where large numbers of people gather, or for responding to disasters, and also as a way to bring communications to remote areas where fiber-optic cables are difficult to lay. Compared to today's mobile phones, which use frequencies in the 0.8-2.0 GHz range, the W band uses a frequency band more than 50 times as broad with 50 times the speed, meaning it is a frequency band that is well-suited to these high-capacity wireless communications.In order to transmit wireless signals over a distance of several kilometers, the transmission antenna needs a power amplifier capable of a high output on the order of several watts. Existing power amplifiers for high-frequency transmissions in the millimeter-wave band (30-300 GHz), which are built using gallium arsenide or CMOS semiconductors, are limited by their operating voltage to an output of about 0.1 W, and it has not been possible to increase this. GaN-HEMT power amplifiers have achieved high output performance in the microwave range (3-30 GHz), but the problem up until now was that their output performance declined in the W-band range. To solve these problems, Fujitsu developed a GaN-HEMT device with a unique structure capable of increasing output in the millimeter band (Figure 1). This uses a layer of indium-aluminum-gallium-nitride (InAlGaN), and double-layer silicon nitride (SiN) passivation film to increase current density by a factor of about 1.4, resulting in 3.0 W of output power from a transistor per 1-mm of gate width, at a high frequency of 100 GHz. In developing this transistor, Fujitsu collaborated with Professor Yasuyuki Miyamoto of the Tokyo Institute of Technology in developing a device-simulation technology.Fujitsu succeeded in developing a power amplifier with the world's highest W-band output performance using this GaN-HEMT device with a proprietary structure (Figure 2). In order to successfully design a power amplifier with high output performance, Fujitsu precisely measured and modeled the characteristics of GaN-HEMT during high-frequency operation. Based on that, a circuit was designed where pairs of GaN-HEMTs were grouped together into compact, high-gain units with low power loss. In order to maximize the power from these units, GaN-HEMTs were connected in a series by the interstage circuit where the signal lines and the device layouts were carefully laid out. Using a model of these compact, high-gain units, Fujitsu conducted simulations to optimize the distributor and combiner matching circuits between the units, and their layouts and signal lines, resulting in a high-amplitude power amplifier (Figure 3). A prototype power amplifier had amplitude that multiplied its input by a factor of 80, producing 1.15 W of output power. Power output per transistor, a measure of power-amplifier performance, was 3.6 W per 1 mm of gate width, the highest in the world.The newly developed power amplifier achieved a 1.8 times increase in power-amplifier output over previous W-band power amplifiers, with the world's highest output performance (Figure 4). This translates to an improvement of over 30% in terms of range for wireless communications at speeds of several gigabits per second.Fujitsu plans to apply this power-amplifier technology to high-capacity long-range wireless communications, and to implement high-speed wireless communications systems that can be used for high-expediency temporary communications infrastructure for use during special events and when fiber-optic links have been broken in the event of disasters.