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Ⅰ IntroductionYou can image this case: If you drive an older vehicle, chances are you don't have Bluetooth. If you don't want to remove your factory stereo to install an aftermarket Bluetooth stereo, a Bluetooth amp is ideal. Not only will you be able to add Bluetooth to your vehicle, but you will also be able to amplify your speakers and improve overall system performance.CatalogⅠ IntroductionⅡ Bluetooth Amplifier Related  Video:Ⅲ What Is A Bluetooth Amplifier?Ⅳ What Is Bluetooth?Ⅴ Why You Need a Bluetooth AmplifierⅥ Common ApplicationsⅦ How Bluetooth Amplifiers Works？Ⅷ Three Things You Need to ConsiderⅨ Recomendation  Bluetooth Amplifiers9.1 Sony STRDH190 2-CH Stereo Bluetooth Audio Amplifier9.2 Pyle Karaoke Wireless Bluetooth Amplifier9.3 Fosi Audio Store BT20A Stereo Audio AmplifierⅩ FAQ   Ⅱ Bluetooth Amplifier Related  Video:Bluetooth AmplifierBluetooth Amplifier Video Description:Amplifier Bluetooth simple cocok buat kamu yang nggak mau ribet, cuma pakai speaker woofer 4-6inch dan 3-4inch buat vocal kamu bisa menikmati musik dengan banyak fitur.  Ⅲ What Is A Bluetooth Amplifier?Understanding technology is a difficult and time-consuming task. Because there is never a shortage of products brought to market. It is a tough task of staying on top. For instance, the Bluetooth headphone amp is such a product that it hasn't been around for very long, it's a good idea to start by defining it.A Bluetooth amplifier is a device that is intended to convert your favorite pair of wired headphones into wireless Bluetooth headphones by utilizing Bluetooth technology's radio frequency communication.Bluetooth AmplifierⅣ What Is Bluetooth?Bluetooth emerged as a technology in Sweden in the late 1990s. Its original goal was to limit the need for unnecessary cable connections between devices from various manufacturers.For example, if you have an Apple smartphone and a JBL or Bose speaker, it may be difficult to transfer an audio signal from one to the other as the two devices use rather proprietary connections.Bluetooth, on the other hand, allows devices to communicate with one another via short-range radio frequencies that alternate hundreds of times per second. This also contributes to security, making Bluetooth connections a very secure way to transfer data.Bluetooth Wireless Technology (BWT) has nearly limitless potential, particularly in the Internet of Things (or IoT), and is now used in smart speakers, smart home implementations, and a variety of other devices.Bluetooth Ⅴ Why You Need a Bluetooth AmplifierStream Music Through Your System Directly from Your AmplifierEliminate the Need of an Expensive Head UnitBoost Your System Ⅵ Common ApplicationsOne of the benefits of using a Bluetooth amplifier is that the device can offer you flexibility. What is more, ，While a Bluetooth amplifier is an excellent addition to your car's sound system, they are also ideal for marine and power sports applications, as well as just about any other application that requires an amplifier.amplifierIn the CarA Bluetooth amplifier is an additional, and possibly the most efficient, way to add Bluetooth to your vehicle. Many older stereos lack built-in Bluetooth simply because it was not a common feature at the time. Until Bluetooth amplifiers were released, the only way to add Bluetooth to your vehicle was to purchase a new, potentially expensive, Bluetooth head unit or a Bluetooth adapter that was compatible with your stereo. With a Bluetooth amplifier, you can kill two birds with one stone. You'll add the convenience of wireless Bluetooth streaming to your vehicle while also enhancing your current system. Some Bluetooth amplifiers also include a wired microphone, allowing you to make hands-free phone calls.On the BoatBluetooth amplifiers aren't just for use in your car; they're also great for listening to music while boating. Many boats don't even have a sound system, so if you want to add one, you'll probably have to build it from the ground up. A marine-rated Bluetooth amplifier eliminates the need for a head unit, saving you money while improving the overall performance of the system. And, just like in a car, if your boat has a sound system but the head unit isn't Bluetooth enabled, a Bluetooth amplifier can save you from having to replace the stereo.On the ATVAnyone interested in outdoor power sports is aware that free space is extremely limited. Because of this, installing a sound system in an ATV, UTV, SSV, or motorcycle can be a difficult task, and any space-saving measures you can take are invaluable. A Bluetooth amp can combine your source unit and amplifier into a single piece of equipment while still allowing you to play music through your system. Ⅶ How Bluetooth Amplifiers Works？ How Bluetooth Amplifiers WorksA Bluetooth amplifier is a very simple piece of equipment. It functions and installs similarly to any other amplifier (they can be connected to a source unit, but it is not required), but it includes an integrated Bluetooth module that allows you to connect virtually any Bluetooth-enabled device (smartphones, tablets, etc.) to it wirelessly. Bluetooth amps eliminate the need for a traditional head unit by allowing the amp to function as both the transmitter and the receiver.  Ⅷ Three Things You Need to ConsiderWatts of amplifier: This number indicates the maximum power output of your amplifier. As the power output of the speakers you're going to connect to your amplifier increases, so should the power output of your amplifier. Otherwise, you won't be able to get good sound quality. The total power output of your amplifier must be greater than or equal to the total power required by all of the speakers you intend to connect to it.Bluetooth version: Bluetooth 5.0 is the most recent Bluetooth version. Obsolete Bluetooth versions are not recommended for purchase because they are difficult to pair and have a limited operating range. Furthermore, you will not experience faster data transfer speeds when compared to the most recent version.Impedance: The impedance of your amplifier determines the quality of music you will hear. It should always be the same as the impedance of your speakers. As a result, always ensure that the impedance of your amplifier is equal to the total impedance of all the speakers you intend to connect to it. Ⅸ Recomendation Bluetooth AmplifiersThere are all kind of Bluetooth Amplifiers and the following three are the most popular at the present. This part will introduce their specifications, pros and cons.9.1 Sony STRDH190 2-CH Stereo Bluetooth Audio AmplifierSony STRDH190 2-CHSONY is without a doubt the best brand in the world when it comes to electronic items. If you are willing to pay a premium, there is no other brand that can compete with the quality of SONY products. Another example is their STRDH190 2-CH HOME STEREO RECEIVER.You can connect two pairs of speakers to it if A/B switching is enabled. With A+B mode, you can also switch between A and B to play speakers separately in two different rooms, or you can play all four speakers at once in the same room. It also has a full-size 14" headphone jack for listening to music through a headset.The STRDH190-2 AMPLIFIER features HI-RES AUDIO, which allows you to hear music as if the artist were performing in front of you. It has a high-capacity transformer that produces clear, distortion-free sound. Its redesigned design reduces transmitted vibrations from speaker sound pressure, providing you with more focused and powerful sound.This amplifier also has an FM RADIO feature. It comes with 30 pre-programmed radio channels. Its remote-control feature allows you to change audio settings from a distance, making you feel less tired and more at ease. The STRDH 190 2-CH Bluetooth amplifier has a low 5 14" height and will easily fit into your A/V cabinets. SpecificationsType: Amplifier with two channelsInput: Bluetooth input/4 RCA inputs/3.5mm aux inputImpedance: 6-16 ohm impedanceMaximum o/p power: 100 watts x 2 Work AC voltage range: 120-230 voltsRemote control and an FM antenna are included as extras.Dimensions: 11x17x5.2inches17 pound weightWarranty period: 12 monthsProsHigh output powerRemote control capabilityConnects to paired Bluetooth devices automatically.The FM tuner automatically searches for channels in your area.ConsLarge size and weightExpensive in terms of price. 9.2 Pyle Karaoke Wireless Bluetooth AmplifierPyle Karaoke WirelessPyle is a leading producer of high-quality home audio, car audio, and Pro Audio DJ speaker systems. To meet the diverse needs of consumers, the American brand creates a wide range of audio systems with advanced features.Pyle's Bluetooth amplifier has a power rating of 500w and is designed for amplifying multiple speakers with impedances ranging from 4 to 8 ohms. Furthermore, the amplifier has four channels, making it ideal for your PA and home theater system. It has Bluetooth version 4.0 and a decent range for pairing with all of the latest smart devices such as smartphones, laptops, and PCs.The Bluetooth amplifier has 7 input ports for a variety of connectivity options. There is a USB port, a micro SD slot, an FM radio, an AUX port, an MP3 slot, an audio port, and a REC. In addition, there is subwoofer output (L/R) connectors and two 14-inch microphone inputs.The amplifier includes a talk-over function for voice-over, announcements, and paging. When you activate the talk-over mode, the audio will be paused so that you can speak. The crisp buttons and rotary knob make the amplifier simple to use. You can adjust the equalization and volume using the rotary knob. The package also includes a remote control for controlling the amplifier from a distance.Despite the fact that the warranty period is not explicitly stated on the product page, all Pyle products come with a one-year warranty from the date of purchase. SpecificationsAmplifier with four channelsBluetooth/FM radio/AUX/two 14-inch microphone inputs/headphone jack/MP3/USB/SD card inputMaximum o/p power: 500 watts20Hz to 20kHz frequency response4 to 8 ohms in impedanceUp to 30 radio station presets are available.>81 dB signal-to-noise ratioRemote control/FM antenna is a unique feature.Dimensions: 13 x 9.84 x 3.54 inches10.3 pounds1-year warrantyProsProvides four channelsRemote control is used to control the unit from a distance.The FM tuner has an LCD.Wireless range of more than 40 feetConsUses an older Bluetooth version 4.0A bit heavy  9.3 Fosi Audio Store BT20A Stereo Audio AmplifierFosi Audio Store BT20AA FOSI product is next on the list of best Bluetooth amplifiers. This time, it's the BT20A amplifier, which has a maximum output of 200 watts. This allows you to use the same amplifier to power two passive speakers of 100 watts each.It has a built-in CSR64215 chip that provides a strong and stable Bluetooth connection with a range of 50 feet. You will enjoy exceptional music clarity thanks to the TPA3116D2 chip, which provides harmonic distortions of less than 0.04 percent even at high volumes.Again, using the bass and treble control knobs, you can adjust the music output to your liking. It also has a built-in power circuit that prevents sparking when you plug in your amplifier, making it safe to use.The sleek curved edges design of the FOSI BT20A is another feature that draws customers in. This allows you to handle it comfortably without experiencing any sharp pain in your palms. SpecificationsClass D, two-channel amplifierBluetooth and RCA inputs are available.2-8 ohm impedanceMaximum o/p power: 2 x 100 watts (200watts max)AC 110-240 volts is the working voltage.24v DC/4.5A power adapterA unique feature is that it includes a Bluetooth antenna.Dimensions: 5.2 x 3.54 x 1.42 in.2.09-pound weightPros18-month warrantyPowerful output.The bluetooth range is greater than that of the bt10a amplifier.Curved round edges are gentle on your hands.ConsThere is no remote control feature. Ⅹ FAQ1. What is a Bluetooth amplifier used for?A Bluetooth amplifier is designed to convert your favorite pair of wired headphones into wireless Bluetooth headphones by harnessing the radio frequency communication of Bluetooth technology.2. Can you connect an amplifier to a Bluetooth speaker?You can connect your receivers to a wireless speaker by using a Bluetooth transmitter. Plug the Bluetooth transmitter into the headphone port of the receiver. Turn on the receiver after plugging it into a power source.3. Is a Bluetooth amplifier worth it?If you can get yourself a decent set of Bluetooth headphones, then the answer to whether or not headphone amps are worth it is a resounding no. ... A headphone amp increases low voltage audio signal from a source device, allowing the signal to be converted into a sound wave by your headphones4. Do I need a Bluetooth amp?Bluetooth headphones will never need an amplifier, as the headphones themselves deliver the power to the drivers internally. Editor's note: this article was updated on June 14, 2021, to expand upon technical information.5. What is a Bluetooth audio amplifier?The product is simple, bluetooth audio transmitter equipment that can be connected to speakers and other devices, play music through bluetooth wireless transmission. ... At the same time, the product is a multifunctional amplifier for bluetooth speakers. 

Introduction The operational amplifier has a non-inverting input terminal and an inverting input terminal in the electronic circuit. The polarity of the input terminal and the output terminal are the same is a non-inverting amplifier, and the polarity of the input terminal and the output terminal are opposite called inverting amplifier. The inverting amplifier circuit has the function of amplifying the input signal as inverting output. Inverting Op Amp and The Concept of Virtual Ground in Op Amp Catalog Introduction Ⅰ Inverting Amplifier Basics Overview 1.1 Working Principle 1.2 Inverting Amplifier Gain Calculator 1.3 Inverting Amplifier Features 1.4 Inverting Amplifier Functions Ⅱ Inverting Amplifier Applications Ⅲ Inverting Amplifier Explain with Diagrams: NE5532 Ⅳ Inverting Amplifier Circuit Design Steps Ⅴ FAQ Ⅰ Inverting Amplifier Basics Overview 1.1 Working Principle As shown in Figure 1, the inverting amplifier circuit has the function of amplifying the input signal as inverting output. "Inverting" means that the positive and negative signs are reversed. This amplifier uses negative feedback technology, which used to return a part of the output signal to the input. In Figure, the wiring method of connecting the output Vout to the inverting input terminal (-) via R2 is negative feedback. Figure 1. Inverting Amplifier Circuit Operational amplifiers have such characteristics. When the power supply voltage is not applied to the output terminal, the non-inverting input terminal (+) and the inverting input terminal (-) are considered to have the same voltage, that is to say, it can be regarded as a virtual short circuit. Therefore, when the positive input terminal (+) is 0V, the voltage at output is also 0V.The input impedance of the operational amplifier is extremely high, and there is basically no current in the inverting input terminal (-). Therefore, when the current flows to R2, the I1 and I2 are basically equal. Based on the above conditions, using Ohm's Law for R2, we get Vout=-I1xR2. I1 is negative because I2 flows from point A where the voltage is 0V. From another point of view, when the input voltage of the inverting input terminal (-) rises, the output will be inverted and amplified greatly in the negative direction. Since the output voltage in the negative direction is connected to the inverting input terminal via R2, the voltage rise of the inverting input terminal (-) will be blocked. Both the inverting input terminal and the non-inverting input terminal voltage become 0V, and the output voltage is stable.   1.2 Inverting Amplifier Gain Calculator Calculate the gain through the relationship between the input and output in this amplifier circuit. The gain of an inverting op amp is the ratio of the feedback resistance to the input resistance, that is, the ratio of Vout to Vin, and the formula is Vout/Vin= (-I1xR2) /(I1xR1)=-R2/R1. The resulting gain is negative, indicating that the waveform is inverting.The current flowing through R1: I1=(Vi-V-)/R1...aThe current flowing through R2: I2=(V--Vout)/R2……bV-=V+=0………………cI1=I2……………………dSolve the above algebraic equations to get Vout=(-R2/R1)*Vi.This is the input and output relationship of the inverting amplifier circuit.   1.3 Inverting Amplifier Features It can reduce the input impedance or keep a certain value.It can be used as a current input type.Virtual short-circuit point is generated at a certain potential.Its positive input port is free.If the signal source impedance is low, it is easier to obtain a required S/N.The magnification is -Rf/R.   1.4 Inverting Amplifier Functions The inverting amplifier is the basic gain stage in the CMOS circuit. It adopts a common source structure, and the load can be an active load or a current source.Advantages: The potential of the two input terminals is always approximately zero (the non-inverting terminal is grounded, and the inverting terminal is virtual ground). With only differential mode signals,it has strong anti-interference ability.Disadvantages: The input impedance is very small, equal to the resistance of the series resistance from the signal to the input.   Ⅱ Inverting Amplifier Applications Figure 2. Basic Inverting Amplifier Circuit 1) As a IntegratorThe original resistor R2 of the inverting amplifier is replaced by a capacitor C2. At this time, the relationship between the input signal Vi and the output signal Vo forms an integral relationship.2) As a DifferentiatorReplace the original resistor R1 of the inverting amplifier with an electric capacitor C. At this time, the relationship between the input signal Vi and the output signal Vo is differential.3) As a AdderIf the inverting amplifier is slightly changed, the relationship between the input signal and the output signal Vo at this time, if R1 = R2 = R3 =...= Rn = Rf, it can be simplified to Vo = -(V1+V2+V3+.. .+Vn), is additive.   Ⅲ Inverting Amplifier Explain with Diagrams: NE5532 The equivalent resistance seen between the input terminal and the ground of the inverting amplifier circuit is equal to the equivalent resistance between the input terminal and the virtual ground, so the input resistance of the circuit is Ri=R. It can be seen that although the input resistance of the ideal operational amplifier is infinite, the input resistance of the inverting proportional arithmetic circuit is not large because of the parallel negative feedback introduced by the circuit. Figure 3. NE5532 Audio Amplfier Circuit In order to increase the input resistance, R must be increased. For example, when the scale factor is -50, if Ri=10kΩ, R should be 10kΩ and Rf should be 500kΩ. If Ri=100kΩ, R should be 100kΩ and Rf should be 5MΩ. In fact, when the resistance in the circuit is too large, on the one hand, due to the process, the stability of the resistance is poor and the noise is large, on the other hand, when the resistance is of the same order of magnitude as the input resistance of the integrated op amp, the proportional coefficient -Rf/R of the circuit will change greatly, and its value will not only be determined by the feedback network. Therefore, it is necessary for practical applications to use a resistor with a smaller resistance value to get a larger scale factor and a larger input resistance.Look at the following two simulations: Figure 4. Current and Voltage Measuring From above, it doesn't matter without R0, take a look at this below. Figure 5. Current and Voltage Measuring Their output is different, if the expected result is -4V. The reading value -3.608V obviously does not meet the design requirements. We now know that the resistance value of Rs in Figure 5 is orders of magnitude greater than the input resistance of the integrated operational amplifier. Next, if have R0, look at the picture below. Figure 6. Current and Voltage Measuring It can be seen from Figure 6 that after adding R0, the output of the op amp is normal. Why is this?In a TTL circuit, the transistor has a bias current, which will produce a DC voltage drop on the feedback resistor of the e pole. Although it is small, the amplifier has a high amplification factor, which affects the output accuracy greatly. A resistor in the same value as the negative terminal is connected to the positive terminal to cancel the effect of the bias current.R0 is a compensation resistor, which minimizes the bias current error to ensure the symmetry of the differential amplifier circuit of the input stage. When its value is u=0 (that is, the input terminal is grounded), the inverting input terminal is always the equivalent resistance, that is, the parallel connection of the resistance of each branch, so R0=Rs/Rf, through Rf in the circuit, induce negative feedback. According to practical experience, it is best to add a compensation resistor to improve the stability of the circuit. Of course, it can be omitted under normal circumstances.   Ⅳ Inverting Amplifier Circuit Design Steps Inverting amplifiers are several commonly used amplifier types. How to use operational amplifiers design inverting amplifier circuit? The following sharing is the detailed steps.Step 1: Determine the magnification.As shown in the figure below, the amplification factor of the inverting amplifier is (-R2/R1). Figure 7. Determine the Magnification Step 2: Determine the supply voltage.Ensure that the output voltage after the input voltage Vin is multiplied by the amplification factor (-R2/R1) will not exceed the power supply voltage. If it is not the rail-to-rail operational amplifier used, it is better to have a margin of 1~2V. Figure 8. Determine the Supply Voltage Step 3: Determine the gain bandwidth product (GBW).If you are amplifying an AC signal, you need to consider the gain bandwidth product. The calculation formula is: bandwidth of input signal × design gain, select an operational amplifier whose GBW is greater than the required one. Step 4: Check the bandwidth with the slew rate (SR).If the amplifying is a large AC signal, there may be insufficient bandwidth, and it may not be accurate enough to calculate based on the gain-bandwidth product.SR = 2*pi*f*Vp -> f = SR/(2*pi*Vp), where Vp: peak output voltage.If the calculated value f is less than the input voltage frequency, the operational amplifier is not suitable and needs to be replaced. The actual bandwidth should be the smaller of the gain bandwidth product and the slew rate. Step 5: Determine the input offset voltage.Since the offset voltage is also a DC signal, if it is to amplify the DC signal, it should be noted that the offset voltage will also be amplified by the corresponding multiple. If the accuracy is high, try to choose an operational amplifier with a small offset voltage. Step 6: Determine the resistance value.In step 1, the ratio of R1 and R2 has been determined. R1 is generally 1k~10k. A small value is prone to cause gain errors, and a larger value will increase noise (resistor thermal noise). R2 takes the resistance value corresponding to the multiple of R1.It is better to choose the chip resistor, because the parasitic parameters are small.R3=R1/R2, if R1 and R2 are connected in parallel, which are not required.   Ⅴ FAQ 1. What is the inverting amplifier?An inverting op amp is an operational amplifier circuit with an output voltage that changes in the opposite direction as the input voltage. In other words, it is out of phase by 180o。   2. What is inverting amplifier and its application?The inverting amplifier is an important circuit configuration using op-amps and it uses a negative feedback connection. An inverting amplifier, like the name suggests, inverts the input signal as wells as amplifies it.   3. How does an inverting amplifier circuit work?In an inverting amplifier circuit, the operational amplifier inverting input receives feedback from the output of the amplifier. Assuming the op-amp is ideal and applying the concept of virtual short at the input terminals of op-amp, the voltage at the inverting terminal is equal to non-inverting terminal.   4. What are the applications of inverting amplifier?op-amp inverting amplifier. Op amp summing amplifier: Based around the inverting amplifier circuit with its virtual earth summing point, this circuit is ideal for summing audio inputs. It is widely used in audio mixer and many other applications where voltages need to be summed.   5. Why is it called inverting amplifier?It is called Inverting Amplifier because the op-amp changes the phase angle of the output signal exactly 180 degrees out of phase with respect to input signal. Same as like before, we use two external resistors to create feedback circuit and make a closed loop circuit across the amplifier.   6. What are the characteristics of inverting amplifier?1) No Current Flows into the Input Terminals.2) The Differential Input Voltage is Zero as V1 = V2 = 0 (Virtual Earth)   7. What is the formula of inverting amplifier?One final point to note about the Inverting Amplifier configuration for an operational amplifier, if the two resistors are of equal value, Rin = Rƒ then the gain of the amplifier will be -1 producing a complementary form of the input voltage at its output as Vout = -Vin.   8. What are advantages and disadvantages of inverting amplifier?Advantages and Disadvantages of Inverting AmplifierIt follows the negative feedback. The gain factor of these amplifiers is very high. The output generated will be out of phase with the applied input signal. The potential values at both the inverting and the non-inverting terminals maintained at zero.   9. What are the advantages of inverting amplifier?The op amp circuit for the inverting amplifier offers many advantages including relatively low input impedance, a low output impedance and the level of gain that is required (within the limits of the op amp and the gain required from the overall circuit.   10. What is the use of inverting amplifier?The inverting amplifier is an important circuit configuration using op-amps and it uses a negative feedback connection. An inverting amplifier, like the name suggests, inverts the input signal as wells as amplifies it.   11. What is mean by inverting amplifier?An inverting amplifier takes an input signal and turns it upside down at the op amp output. When the value of the input signal is positive, the output of the inverting amplifier is negative, and vice versa. ... The amount of amplification depends on the ratio between the feedback and input resistor values.   12. How an opamp is used as inverting amplifier?Theory: An inverting amplifier using opamp is a type of amplifier using opamp where the output waveform will be phase opposite to the input waveform. The input waveform will be amplifier by the factor Av (voltage gain of the amplifier) in magnitude and its phase will be inverted.   13. What is an inverting amplifier used for?op-amp inverting amplifier. Op amp summing amplifier: Based around the inverting amplifier circuit with its virtual earth summing point, this circuit is ideal for summing audio inputs. It is widely used in audio mixer and many other applications where voltages need to be summed.   14. How does an inverting amplifier work?An inverting amplifier takes an input signal and turns it upside down at the op amp output. When the value of the input signal is positive, the output of the inverting amplifier is negative, and vice versa.   15. What is the gain of an inverting amplifier?The gain of inverting amplifier is Av= – Rf/Ri.

Introduction The audio power amplifier, also called power amp, is a sound-producing device that reconstructs the input audio signal on the output element. The reconstructed signal volume and power level must be idea, effective and low distortion. The audio frequency range is about 20Hz to 20000Hz, so the amplifier must have a good frequency response in this range. Depending on the application, the power level varies greatly, from the milliwatt level of earphones to the several watts of TV or PC audio, to the tens of watts of home stereo and car audio, to the more powerful home and commercial audio, even the system’s hundreds of watts are large enough to meet the sound requirements of the movie theater or auditorium. Catalog Introduction Ⅰ What is Audio Power Amplifier? Ⅱ Types of Audio Power Amplifiers 2.1 Class A Power Amplifier 2.2 Class B Power Amplifier 2.3 Class AB Power Amplifier 2.4 Class D Power Amplifier Ⅲ Audio Power Amplifiers Comparisons Ⅳ Audio Power Amplifier Circuit Architecture Ⅴ Typical Audio Amplifier Circuits Examples Ⅵ FAQ Ⅰ What is Audio Power Amplifier? Audio power amplifier is one of the important components of multimedia products and is widely used in the field of consumer electronics. Linear audio power amplifiers have always dominated the traditional audio amplifier market due to their low distortion and good sound quality. With the popularization of portable multimedia devices such as mobile phones, tablet PC, and notebook computers, the efficiency and volume of linear power amplifiers can meet the requirements of the market, for example, class D power amplifiers have become more and more popular for their advantages such as high efficiency and small size.The development of audio amplifier has experienced three generations of electron tube (vacuum tube), bipolar transistor and field effect tube. The tube audio amplifier has a mellow tone, but it is bulky, with the disadvantages of high power consumption, extremely unstable, and poor high-frequency response. Bipolar transistor audio amplifiers have bandwidth, large dynamic range, high reliability, long life, and high-frequency response, but its static power consumption and on-resistance are very large, so it is difficult to improve its efficiency. The FET audio amplifier has the same mellow tone as the electronic tube, and its dynamic range is wide, and more importantly, its on-resistance is small, which can achieve very high efficiency. audio power amplifier" width="410" height="250" /> Figure 1. Hi-Fi Audio Power Amplifier Ⅱ Types of Audio Power Amplifiers There are many types of audio power amplifiers, and more than ten modes of it commonly used, such as Class A, Class B, Class AB, Class C, Class D, Class E, Class F, Class G, Class H, and Class S, but only four types suitable for audio applications: Class A, Class B, Class AB and Class D. 2.1 Class A Power Amplifier The main feature of the Class A power amp is: The operating point Q of the amplifier is set near the midpoint of the load line, and the transistor is turned on during the entire cycle of the input signal. The amplifier can work in a single tube or push-pull state. Since the amplifier works in the linear range of the characteristic curve, transient and alternating distortion are small. The circuit is simple and the debugging is convenient. Class A power amplifiers only need one transistor to provide current to the load, and the conduction angle is 360°C during a complete signal cycle. This kind of power amplifier has low distortion, but often requires a large static current and is low in efficiency. Theoretically, the maximum working efficiency of a class A power amplifier is 25%, so a heat sink is required when working. 2.2 Class B Power Amplifier Class B power amplifier is composed of two complementary transistors. In a complete signal cycle, each amplifier tube will be turned on in one half cycle and turned off in the other half cycle, that is, the conduction angle is only 180°C. Because it has no static current, it has a higher efficiency. In theory, the maximum efficiency of a Class B power amplifier can reach 78%. However, when the input signal is close to zero, the amplifier tube has a critical conduction state, resulting in crossover distortion. 2.3 Class AB Power Amplifier Class AB power amplifier inserts two diodes into the input end of the Class B power amplifier. When the input is close to zero, the amplifier tube has been slightly turned on, so that the conduction angle of each amplifier tube is greater than 180°C and less than 360°C. It overcomes the crossover distortion of Class B power amplifiers, and the efficiency is between Class A and Class B power amplifiers, based on a common structure of traditional linear power amplifiers. However, the medium output voltage is usually far away from the power supply voltage, and a lot of power consumption is consumed in the transistor. Therefore, even a well-designed amplifier, its efficiency is still low. 2.4 Class D Power Amplifier Class D (digital audio power) power amplifier is a kind of input analog audio signal or PCM digital information into PWM (pulse brightness modulation) or PDM (pulse density modulation) pulse signals, which is used to control the amplifier power switching devices turn on/off audio power amplifiers, also known as switching amplifiers. It has the outstanding advantage of high efficiency.The output stage of the Class D power amplifier consists of two complementary power tubes. Driven by the high-frequency control pulse signal, the power tubes work in the on-off state. One is turned on and the other is turned off. Therefore, the amplifier does not require static power consumption, that is, it has a very high efficiency. In theory, the efficiency of Class D power amplifiers can reach 100%, but in fact it is over 80%, which is 2 to 3 times that of traditional linear power amplifiers.The digital audio power amplifier also looks like a one-bit power digital-to-analog converter. The amplifier is composed of four parts: input signal processing circuit, switching signal forming circuit, high-power switching circuit (half-bridge and full-bridge) and low-pass filter (LC). In electronics, Class D amplifiers use a very high frequency switch circuit to amplify the audio signal. DIY Class D Audio Amplifier Class D amplifiers have the following advantages:1) It has a high efficiency, usually above 85%.2) Small size, which can save a lot of space than analog amplifier circuits.3) Connection without crack noise.4) Have low distortion and good frequency response curve. Few peripheral components, easy to design and debug.   Ⅲ Audio Power Amplifiers Comparisons 1) Class A, B, and AB amplifiers are analog amplifiers, and class D amplifiers are digital amplifiers. 2) Class B and Class AB push-pull amplifiers have higher efficiency and less distortion than Class A amplifiers, and their transistors consume less power and have better heat dissipation. However, Class B amplifiers will have poor switching characteristics during the transition between transistor on and off states or cause alternate distortion due to improper selection of circuit parameters. 3) The Class D amplifier has high efficiency and low distortion, a good frequency response curve, and fewer peripheral components. 4) Class AB amplifier and Class D amplifier are the basic circuit forms of audio power amplifiers at present. Figure 2. Amplifier Circuit Example Ⅳ Audio Power Amplifier Circuit Architecture The purpose of audio amplifier is to reproduce the audio input signal with high efficiency and low distortion on the sound output element at the required volume and power level. The frequency range of the audio signal is 20 Hz to 20000 Hz, so the audio amplifier must have a good frequency response. Audio amplifiers usually consist of preamplifiers and power amplifiers.PreamplifierThe amplitude of the audio signal source signal is generally very small and cannot directly drive the power amplifier. Therefore, they must be amplified to a certain condition first, which requires the use of a preamplifier. In addition to the signal amplification function, it can also have functions such as volume adjustment, tone control, loudness control, and channel equalization.Power amplifierThe power amplifier is referred to as the power amplifier for short, and its purpose is to provide the load with a large enough current drive capability to achieve power amplification. Class D power amplifier works in the on-off state. In theory, it does not require static current and has high efficiency.The topological structure of a typical Class D power amplifier circuit is shown in Figure 2: It consists of a triangle wave generator, a comparator, a power output stage and an LC low-pass filter. Figure 3. Class D Power Amplifier Circuit Figure 2 is a schematic diagram of the working principle of a Class D power amplifier. The sine wave audio input signal and the triangular wave signal with a much higher frequency are modulated by the comparator to obtain a PWM modulation signal whose duty cycle is proportional to the amplitude of the input signal. It pushes the output power tube to work in the on-off state. The output end of the tube obtains an output signal with a constant duty cycle. The amplitude of the output signal is the power supply voltage and has a strong current drive capability. After signal modulation, the output signal contains both the input signal and the fundamental component of the modulated triangle wave, as well as their higher harmonics and combinations. After LC low-pass filtering, the high-frequency components in the output signal are filtered out, and a low-frequency signal with the same frequency and amplified amplitude as the original audio signal is obtained on the load.   Ⅴ Typical Audio Amplifier Circuits Examples The following is a brief introduction of AN7115 audio power amplifier circuit. Figure 4. AN7115 Audio Amplifier Circuit AN7115 has an output power of 2.1W and a noise output of 3mV under the conditions of V=9.0V, THD=10%, and RL=8Ω.Limit parameters: Vcc=13V, power dissipation (without radiator) is 1.2W, and 2.25W with a radiator. Working temperature: -20℃ to 70℃, suitable for small portable radio recorders and audio equipment as power amplifiers. TDA2030 adopts V-shaped 5-pin single in-line plastic package structure. According to the shape of the pin, it can be divided into H-type and V-type. This integrated circuit is widely used in car stereo radio and tape recorders and mid-power audio equipment. It has the characteristics of small size, high output power, low distortion, etc., and has an internal protection circuit. Circuit characteristics are as followed: Figure 5. TDA2030 Audio Power Amplifier Circuit 1) Very few external components.2) The output power is large, Po=18W (RL=4Ω).3) The use of ultra-small package (TO-220) can increase the assembly density.4) The boot impact is minimal.5) It contains various protection circuits, so it is safe and reliable to work. The main protection circuits include: short circuit protection, thermal protection, ground wire coupling open circuit, power supply polarity reverse connection (Vsmax=12V), and load discharge voltage kickback, etc. Figure 6. Mini Audio Power Amplifier Ⅵ FAQ 1. What is audio power amplifier?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. Audio power amplifiers are found in all manner of sound systems including sound reinforcement, public address and home audio systems and musical instrument amplifiers like guitar amplifiers.   2. How do audio amplifiers work?An amplifier takes an input signal from a source, such as a laptop, turntable or CD player, and creates a larger copy of the original signal before it's sent to the speakers. It gets the power to do this from your mains electricity, which is sent directly to the power supply within the amplifier.   3. What does an audio power 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.   4. What is the most powerful audio amplifier?Classic audio brand McIntosh has announced its most powerful integrated amplifier. The fully loaded, hybrid MA12000 Integrated Amplifier is McIntosh's most powerful integrated amplifier ever offering 350W per channel.   5. Do you need amplifier for speakers?Powered speakers do not need an amplifier. They have an amplifier already installed in them which is why they are called 'powered speakers' to begin with. Depending on the speakers' input options, you can hook them up to different audio sources without the need for a separate amplifier.   6. Does an amplifier improve sound quality?Amplifiers ideally amplify audio signals linearly and, therefore, do not technically improve or worsen sound quality. However, less-than-ideal amplifiers, amp settings and amplifier-speaker combinations may worsen sound quality. Amps are nevertheless needed to drive speakers and headphones properly.   7. Why do I need a power amplifier?Some users prefer to separate input switching and AV processing from the task of providing power for, and connection of, loudspeakers through separate AV preamp/processors and power amplifiers. ... A separate preamp and power amp results in more equipment and cable clutter.   8. Which is better power amplifier or integrated amplifier?A preamplifier / power amp does generally offer better quality; while flat output has become common place, keeping your switching circuitry separate from your amplification and having two separate power supplies can reduce the internal interference that can be introduced into your signal.   9. What is a home audio amplifier?A home theater amplifier (also known as an audio-visual receiver or simply an AVR) is a powerful piece of kit that combines amplifiers and digital signal processors to convert output from a range of source devices into high quality sound and video. In short, it is the hub of a home theater set up.   10. What is the most powerful audio amplifier?Classic audio brand McIntosh has announced its most powerful integrated amplifier. The fully loaded, hybrid MA12000 Integrated Amplifier is McIntosh's most powerful integrated amplifier ever offering 350W per channel.   11. What is the purpose of an audio amplifier?The goal of audio amplifiers is to reproduce input audio signals at sound-producing output elements, with desired volume and power levels—faithfully, efficiently, and at low distortion.   12. What do you mean by audio amplifier?Any electronic device that increases the power of an electrical signal whose vibrations are confined to the audio frequency range—the range that can be perceived by the human ear—is an audio amplifier.

IntroductionDo you know buffer amplifier or isolation amplifier? The operational amplifier is an extremely efficient and versatile device. As we all known, the op amp is a component that amplifies the weak signal, which can be made into different forms according to the circuit requirements, and the voltage follower is one of them. Most voltage follower circuit will use an Op-amp. A follower is specifically an op amp wired to have a gain of +1. IE, the output is the same polarity and voltage as the input. That is, the output signal is exactly the same as the input signal. Here op amp voltage follower is used to isolate the signal and enhance load capacity. Op-amp as Voltage FollowerIntroductionⅠ Voltage Follower OP AmplifierⅡ Voltage Follower Characteristics2.1 Op Amp Impedance Matching2.2 Buffer Amplifier & Isolation AmplifierⅢ Op Amp Follower Circuit Analysis3.1 Op Amp Voltage and Load3.2 Op Amp Voltage Follower Stability3.3 Op Amp Phase Difference Problem3.4 Adding Feedback ResistanceⅣ Op Amp Voltage Follower ApplicationⅠ Voltage Follower OP AmplifierThe op amp follower sacrifices the voltage amplification factor in exchange for the performance of increasing the input impedance and reducing the output impedance. Because the gain of the op amp is extremely high, the input impedance of the op amp follower tends to be infinite, and the output impedance tends to zero. Within the rated output current range, the feedback voltage is equal to the output voltage, the output voltage is in phase with the input voltage, and the output voltage is slightly smaller than the input voltage. It should be noted that voltage follower is a special case of negative feedback amplifier (voltage series).Op amp voltage follower is actually a simple circuit structure which play a role in impedance matching. When a weaker signal is used to drive a relatively high current, voltage follower is often added in the middle, so that it can make weak signal stronger. It improves the load capacity to a considerable extent, while ensuring that the waveform and amplitude of the signal remain unchanged.For example, a single-chip microcomputer outputs a PWM signal to control LED lights. One LED does not require much current, so there is generally no big problem, however, when multiple LEDs need to light, current may definitely not large enough. If the current output is not enough, which may affect the signal output by the single-chip microcomputer, in this way, the voltage follower comes in handy.Ⅱ Voltage Follower Characteristics2.1 Op Amp Impedance MatchingWhen the op amp gain is approximately 1, that is, the magnification is approximately 1. The "follow" in the follower means that the voltage remains unchanged before and after, and the output waveform is almost not lost. It can be composed of transistors or operational amplifiers (best). Because the op amp input impedance is large and the output impedance is small, voltage follower can reduce the impact on the signal and improve the load capacity.2.2 Buffer Amplifier & Isolation AmplifierHere is a question, how to understand the buffering effect? Is the voltage of the former having a small impact on the back circuit? No, it is equivalent to a constant voltage source. Within the design requirement, no matter how the circuit connected to the subsequent stage changes, the output voltage is constant and does not change. In this way, the magnification or other performance of the previous stage can be kept unchanged. Otherwise, if the previous-stage input impedance is large, and the latter stage is small, the signal will definitely be distorted. For example, if a sinusoidal voltage waveform with a peak value of 10V, the sinusoidal peak value loaded to the latter stage may only be 8V. After adding a voltage follower, the waveform loaded on the input of the voltage follower will basically not change, and the input-output stage voltage ratio is very close to unity. So there will be no distortion.Since the output impedance of the voltage amplifier is generally relatively high, usually in the range of several kiloohms to tens of kiloohms. If the input impedance of the subsequent stage is relatively small, part of the signal will be lost in the output resistance of the previous stage. At this time, a voltage follower is needed to buffer from it. Another advantage of applying a voltage follower is that the op amp input impedance is increased, so that the capacity of the input capacitance can be greatly reduced, which provides a prerequisite guarantee for the application of high-quality capacitors.Another question, what about isolation? Because the op amp input impedance of the voltage follower is very large, it can be approximated as an open circuit. Of course, this open circuit is for the previous circuit. In this case, the previous circuit will not affect the subsequent circuit. However, "open circuit" means what, is it really open? No, the previous voltage is transmitted, but the corresponding current is not transmitted. This is the isolation effect.For example, if the MCU outputs a PWM waveform, you want to use it to control the brightness of a small light bulb. However, the output capacity of the IO port of the general MCU is limited. You can directly use the PWM output from the IO port to drive one light bulb. More than one doesn't work. In this case, you can add a voltage follower, so that the voltage is still the original voltage, but the driving ability has improved. Of course, the output capacity is not increased out of thin air, but comes from the input power of the op amp. In electronics, the diode has current amplification capability, and its source of amplification capability also comes from the power supply.In Hi-Fi circuits, the controversy about negative feedback has been around for a long time. In fact, if there is no negative feedback, most amplifying circuits will not work well. However, due to the introduction of a large loop negative feedback circuit, the back EMF of the speaker will pass through the feedback circuit and be superimposed with the input signal. The sound quality is blurred and the clarity is reduced. Therefore, some of the final stages of the power amplifier adopt a circuit without large loop negative feedback, trying to eliminate the disadvantages by disconnecting the negative feedback loop. However, since the operating current of the final stage of the amplifier varies greatly, its distortion is difficult to control. Here, the function of the voltage follower is just for the application. Putting the circuit between the front stage and the power amplifier can cut off the interference effect of the back electromotive force of the speaker on the front stage, so that the clarity of the sound quality is greatly improved. Ⅲ Op Amp Follower Circuit Analysis3.1 Op Amp Voltage and LoadFigure 1. Op Amp Voltage Follower SchematicThe output and the inverting input terminal are connected in series with a 10k resistor to ensure excellent characteristics. An ac signal is input at the non-inverting input terminal. Of course, dc and ac are all okay, so you will get a very high voltage at the output terminal. AC voltage that is similar and has excellent load capacity, with buffering and isolation effects.3.2 Op Amp Voltage Follower StabilityThe problem of using a voltage follower to keep the operational amplifier stable, that is, how to reduce the oscillation in the amplifier circuit using negative feedback to maintain stability, there is still no final conclusion. The ideal operating state of the op amp is that the output voltage and the input voltage are in phase, that is, when the applied voltage at the negative input causes the output to increase, the op amp can reduce the increased voltage accordingly. However, there is always a difference in phase between the input and output in reality. When the phase difference between the output and the output is 180°, the negative input and the positive input are exactly the same, but the output that should have been reduced is enhanced. It becomes a state of positive and negative collapse. If it falls into this state in a specific frequency band and still maintains the original amplitude, then the output frequency and oscillation state will continue.Figure 2. Feedback Loop3.3 Op Amp Phase Difference ProblemThe main reason for the phase difference between the input and the output:1) Due to the inherent characteristics of op amps.2) Due to the characteristics of the other feedback loop in circuit.Figure 3. Gain-frequency, Phase-frequency CurveFig 3(a), Fig 3(b)and Fig 3(c) respectively represent the voltage gain-frequency characteristic and phase-frequency characteristic of the operational amplifier. As shown in the figure, the voltage gain and phase vary with frequency. The difference between the op amp gain and the gain after feedback (0dB when using a voltage follower) is the gain (feedback gain) of the feedback loop. If the feedback gain is less than 1 time (0dB), then, the phase changes by 180° and returns to the positive feedback state, the negative gain will gradually attenuate in the circuit and theoretically will not cause oscillation.On the contrary, when the phase changes by 180°, if the loop gain corresponding to the frequency is 1 time, the original amplitude will be maintained. If the loop gain corresponding to the frequency is greater than 1, the amplitude will gradually diverge. In most cases, in the process of amplitude divergence, the amplitude is limited due to the influence of nonlinear elements such as the maximum output voltage, and the oscillation state will be maintained.Therefore, the difference between the phase corresponding to the frequency when the loop gain is 0dB, 180° is an important factor for judging the stability of the negative feedback loop, and this parameter is called the phase margin. Unless otherwise specified, when a single amplifier is used as a voltage follower, sufficient phase margin must be maintained (Fig 3b.).3.4 Adding Feedback ResistanceWhen the operational amplifier is used as a follower, when the internal resistance of the signal source is large, adding a feedback resistor with the same resistance as the internal resistance of the signal source can reduce the output offset voltage and improve the follow accuracy. The follower with feedback resistance has a certain current limiting protection effect on the circuit when the circuit is "blocked", which is its advantage.The voltage follower is originally a non-inverting operational amplifier. One of the common features of it is that a common-mode voltage is added to the non-inverting terminal and the inverting terminal.Once this common-mode voltage exceeds the allowable common-mode input voltage range, for example, if the inverting terminal signal is too large, it will cause the input stage transistor to saturate. The inverting terminal signal will be directly added to the second stage of the op amp, making the inverting input becomes non-inverting input, that is, negative feedback becomes positive feedback, and the output signal passes through the feedback loop to further saturate the input stage transistor. As a result of this, the amplifier is of course no longer in normal working condition. Even if the input signal is canceled, it will not immediately return to the normal state. This phenomenon is called blocking.When it occurs, if the feedback loop resistance is not large enough, the current in the feedback loop may burn the input stage transistors and even harm the second stage. In order to avoid blocking, in addition to choosing an op amp with a large common-mode input voltage range, a clamp circuit is often added to the input of the amplifier to ensure that the common-mode voltage at the input does not exceed the allowable range.Of course, in a small-signal inverting operational amplifier, especially in circuits with capacitive elements such as integrating operational amplifiers, blocking may also occur. The processing method is the same as that of the non-inverting amplifier. Ⅳ Op Amp Voltage Follower ApplicationIn many typical circuit designs, there will be an op amp follower before the AD converter. Whether this follower is necessary or not depends on the requirements of the circuit based on the understanding of the function of the follower. First analyze the role of the voltage follower here:The function of the voltage follower here is impedance transformation.Impact 1: The input impedance becomes very high, so that the impact on the input signal can be small.Impact 2: The output impedance becomes very low, and the impact of AD input impedance on the input signal can be very small.It can be seen that the follower is very meaningful. Secondly, analyze your own circuit and the signal under test to make a decision whether to use a follower. Here are some rules to confirm:1) If the output impedance of the signal is very small, then the Impact 1 can be ignored.2) If the input impedance of AD converter is very large, then two impacts can be ignored.3) If both impacts can be ignored, no voltage follower is necessary.4) If there is an impact, a voltage follower is needed. Frequently Asked Questions about Op Amp Voltage Follower1. Which amplifier is called as voltage follower Why?This means that the op amp does not provide any amplification to the signal. The reason it is called a voltage follower is because the output voltage directly follows the input voltage, meaning the output voltage is the same as the input voltage. 2. What is the use of voltage follower?A voltage follower can be used as a buffer because it draws very little current due to the high input impedance of the amplifier, thus eliminating loading effects while still maintaining the same voltage at the output. 3. What do you mean by voltage follower circuit?A voltage follower is also known as a unity gain amplifier, a voltage buffer, or an isolation amplifier. In a voltage follower circuit, the output voltage is equal to the input voltage; thus, it has a gain of one (unity) and does not amplify the incoming signal. 4. What is an op amp buffer?An op-amp voltage buffer mirrors a voltage from a high-impedance input to a low-impedance output. 8 min read. A voltage buffer, also known as a voltage follower, or a unity gain amplifier, is an amplifier with a gain of 1. It's one of the simplest possible op-amp circuits with closed-loop feedback. 5. What is an op amp buffer circuit used for?A buffer is a unity gain amplifier packaged in an integrated circuit. Its function is to provide sufficient drive capability to pass signals or data bits along to a succeeding stage. Voltage buffers increase available current for low impedance inputs while retaining the voltage level.

For so many years, tube amplifier has always been a “controversial” component in the electronic field, people are attracted by its premium sound quality but discouraged by its price.   Today we are going to talk about tube amplifiers, to understand what this device is, why its price is so much higher than other amplifiers, what are its advantages and disadvantages compared with other amplifiers, and so on. Catalog I. What is a Tube Amplifier? II. Pros and Cons of Tube Amplifier? III. How Does the Tube Amplifier Work? IV. Tube Amplifier VS Solid State Amplifier? V. Tube Amplifier VS Transistor Amplifier? VI. Things Needing Attention While Using a Tube Amplifier VII. Why is Tube Amplifier So Expensive? Is It Worth It? VIII. How to Extend the Life of   the Tube Amplifier?    FAQ I. What is a Tube Amplifier? The tube amplifier is one of the earliest electrical signal amplifiers.   The cathode electron emission part, the control grid, the acceleration grid, and the anode (panel) lead enclosed in a glass container (generally a glass tube) are welded to the tube base.   The electric field is used to inject an electronic modulation signal into the control grid in the vacuum, and the signal data of different parameters after signal amplification or feedback oscillation is obtained at the anode.   Tube amplifiers were used in electronic products such as televisions and radio amplifiers in the early days. In recent years, they have been gradually replaced by amplifiers and integrated circuits made of semiconductor materials. However, in some high-fidelity audio equipment, tube amplifiers with low noise and high stability coefficient are still used. II. Pros and Cons of Tube Amplifier? Pros: 1. The tube amplifier has a large input dynamic range and a fast conversion rate.   2. Electronic tube amplifiers mostly use discrete components, manual wiring, and welding, which are low in efficiency and high in cost. This is especially obvious in developed countries.   3. The open loop index of the tube amplifier is better than that of the transistor amplifier. It does not need deep negative feedback and can work stably without adding phase compensation capacitors, so its dynamic index is better.   4. The sound quality of the tube amplifier is generally soft and pleasant. More specifically, the low-frequency sound of the tube amplifier is soft and clear, and the high-frequency sound is slender and clean. The performance of human voice is its strong point.   5. The treble of the tube amplifier is smoother, has enough air, and has a sound coloring that quite a few people like. The soft and slightly fuzzy sound is very beautiful.   6. The tube amplifier mainly causes even-numbered second harmonics. This harmonic component is very pleasing, just like adding rich overtones and beautifying the sound.   Cons: 1. The service life of the tube amplifier is relatively low, and some technical indicators will drop significantly after one to two thousand hours of use.   2. The tube amplifier consumes high power and often works in Class A state, which reduces the efficiency. However, there are basically no harmful sound quality factors such as transient intermodulation distortion, switching distortion and crossover distortion.   3. The tube amplifier is not at all superior to the transistor amplifier in terms of weight, efficiency, and lifespan.   4. In use, the tube amplifier should have good ventilation and heat dissipation. Overheating of the temperature will inevitably shorten the life of the tube amplifier, so it is necessary to keep the temperature of the tube amplifier as low as possible.   5. Vibration is not good for tube amplifiers, so it is important to take anti-vibration measures to avoid vibration as much as possible. III. How Does the Tube Amplifier Work? This is a basic overview of some of the components of a tube guitar amp and how they work, without getting too technical. IV. Tube Amplifier VS Solid State Amplifier? A solid-state amplifier converts an electrical signal into an audio wave using transistor circuitry. Instrumental amplifiers have two amplification stages: the preamp stage at the beginning of the circuit and the power amp stage at the end.    The physical difference between a solid-state amp and a tube amp is that a solid-state machine employs electronic transistors for amplification, whereas a tube amp employs vacuum tubes (also known as valves). Transistors differ from tubes in that they do not deform pleasantly when pushed to their limits.   The key difference between tube amplifier and solid state amplifier is: solid-state amplifiers are ideal for guitarists that require a lot of power (a.k.a a loud, clean, undistorted signal). However, without any natural distortion, an electric guitar can sound brittle. As a result, solid-state amplifiers are more popular among bassists and keyboard players than guitarists. Compared with tube amp, solid-state amp has several advantages: 1.    They are less expensive. Almost all solid-state amplifiers are less expensive than tube amplifiers. They have fewer parts and the ones they do have are reasonably inexpensive.  2.    They are less bulky. Weight can be an issue if you're a gigging musician who needs to transport an amp around town. Tube amplifiers are almost always heavier than solid-state amplifiers. This is due to the circuitry necessary to operate the glass tubes, not the glass tubes themselves (which are hollow). 3.    They require less maintenance. Tube amplifiers need routine maintenance. Most gigging guitarists replace their power tubes once a year and their preamp tubes every two years. Solid-state amplifiers, on the other hand, do not require part switching. They can function for decades with all of their original components. V. Tube Amplifier VS Transistor Amplifier? A transistor amplifier, as the name implies, is used to amplify power, voltage, or current signals. It has a common emitter amplifier, a common collector amplifier, and a common base amplifier. This is the most basic. There are also differential, push-pull, and so on. The audio is actually a power (transistor) amplifier. The difference between transistor amplifier and tube amplifier: 1. Working characteristics and circuit structures are different Transistor amplifiers work under low voltage and high currents. The working voltage of transistor power amplifiers is within tens of volts, and the current reaches several amperes or tens of amperes. In the circuit design, direct-coupled (OCL, BTL, etc.) non-output transformer circuits are mostly used. The output power can be very large, up to several hundred watts, and the various electrical properties are very high. The tube amplifier works under high voltage and low current conditions. The screen voltage of the final power amplifier tube can reach 400-500V or even thousands of volts, and the current flowing through the electron tube is only tens of milliamps to hundreds of milliamps. The input range is too large and the conversion rate is fast. Most of the tube amplifiers use discrete components, manual wiring, and welding, which are low in efficiency and high in cost. Transistor amplifiers mostly use a combination of transistors and integrated circuits, and printed circuit boards are widely used, with high efficiency, stable soldering quality, and high electrical performance indicators. 2. Power reserve and anti-overload ability are different The dynamic range of the high-fidelity amplifier should be 120dB, so as to meet the needs of the sound from the slightest to the peak of the climax, the amplifier output is not clipped, so the amplifier must have sufficient power reserve. If the dynamic range of the audio voltage is 3:1, since the power is proportional to the square of the voltage, the power dynamic range is 9:1. That is to say, a power amplifier with a power of 90W can only be turned on to 10W to achieve high-fidelity playback. Therefore, the transistor amplifier needs a large power reserve to avoid overload distortion. Once the ground is loaded, its distortion will almost rise in a vertical line, which can damage the transistor in severe cases. The anti-overload capability of the tube amplifier is far stronger than that of the transistor amplifier. In case of overload, the peak of the music signal only becomes slippery than the normal waveform, and the sound is not deformed much. For transistor amplifiers, clipping will occur at this time, and the sound quality will deteriorate significantly. 3. Efficiency, life, and cost are different Tube amplifiers are not superior to transistor amplifiers in terms of weight, efficiency, and lifespan. The service life of the electron tube is relatively low, and some technical indicators will drop significantly after one to two thousand hours of use. The lifetime of transistors and integrated circuits is much longer. In addition, the tube amplifier consumes high power and often works in the Class A state, which reduces the efficiency. However, there are no harmful sound quality factors such as transient intermodulation distortion, switching distortion, and crossover distortion. In terms of cost, for the same grade of amplifiers, tube amplifiers are generally significantly higher than transistor amplifiers. The main reasons are the high cost of electronic tubes and output transformers, and the production process of electronic tube power amplifiers is not easy to automate, and the production efficiency is low. 4. Different sound quality The sound quality of the tube amplifier is significantly better than that of the transistor amplifier. Transistor power amplifiers have a sense of overwhelming when listening to high and medium and high frequencies, and less low frequencies. Transistor power amplifiers sound hard, especially low-frequency sounds are not soft enough, and high-frequency sounds are sharp and dry. Sometimes it sounds like there is crossover distortion in the high-frequency range. These phenomena become more obvious when the frequency increases and the volume is louder. However, the transistor amplifier has large dynamics and high speed, which is especially suitable for music with greater dynamics. As for the sound effects of guns and lightning, it is certainly better than a tube amplifier. Generally speaking, the sound quality of the tube amplifier is soft and pleasant. Specifically, the low-frequency sound of the tube amplifier is soft and clear, and the high-frequency sound is slender and clean. The performance of the human voice is its strong point, and therefore it is more valuable. All in all, the choice of amplifier varies from person to person. If you like orchestral music, especially chamber music and vocals, then tube amplifiers should be your first choice. If you like jazz, rock, and modern music, then transistor amplifiers are the choice. VI. Things Needing Attention While Using a Tube Amplifier? 1.    The tube amplifier must be used under the limit parameters. Although it can still work normally under the limit parameters, the life of the tube amplifier will be shortened quickly. Therefore, the tube should be used under the rated parameters. 2.    The location of the components in the device should be conducive to the heat dissipation of the tube amplifier. To control the temperature of the tube case of the tube amplifier, the allowable temperature of the glass case of various tube amplifiers is different. For example, the allowable limit temperature of the power output tube during operation does not exceed 90°C in principle. 3.    Except for the high-reliability tube amplifier with a special structure that can work at higher accelerations, other receiver amplifier tubes can only withstand small shocks for a short time. Therefore, pay attention to the shock absorption of the tube when using it. 4.    When using small tubes (thumb-finger type) and other tubes without tube bases (but with tube needles), use tube sockets specified by the Ministry of Electronics Industry. Prevent cracking or damage to the glass shell. When plugging and unplugging the tube, its direction should be perpendicular to the plane of the tube base. When inserting an electronic tube, prevent damage to the normal position of the contact reed in the socket socket of the tube socket, and avoid using the empty foot of the tube socket as a connecting pad. 5.    When using an indirectly heated tube amplifier, the potential difference between the cathode and the filament must not exceed the specified limit. For this reason, a dedicated filament transformer is often used for power supply. In order to eliminate the effect of leakage current instability, under the condition of not hindering the operation of the circuit, a shunt resistance of about several ohms can be connected between the cathode and the filament. VII. Why is Tube Amplifier So Expensive? Is It Worth It? In short, tube amplifiers are costly because they use pre and power tubes as their primary amplification source. Each tube costs approximately $50 and can have up to four of them in a single unit. Second, these amplifiers have more expensive components, larger casings, and more complicated circuitry than solid-state amplifiers.   Whether tube amplifiers are "worth it” or not, well, that’s more of a subjective question.   If your goal is to build a pristine audio chain that cleanly reproduces the input signal you give it, a tube amplifier is definitely not worth it. By spending extra money to put a tube in your signal chain, you are intentionally distorting the sound.   Note that modern high end A/D/A conversion equipment (which aims for perfect signal reproduction) never uses tubes. The marketing pitch on tube equipment is that it does change the sound that you give it. Don't buy a tube amplifier unless that is what you want.   Now, if your goal is not to amplify signal accurately, but rather to make a sound that you personally find pleasing, a tube may yield some benefits.   You can listen to some tube amps at different levels to decide what you personally prefer. Does this make a tube amp worth it? Bear in mind that there are many ways of creating harmonic distortion (in the analog domain, or emulated with digital techniques), and many are cheaper than tubes, which are expensive to produce.   The high cost of tubes is not a function of the fact that it was difficult to engineer their particular audio qualities. The way tube amplifiers color audio is a historical function of the fact that engineers were not able to compensate for the changes they introduce.   Many people have now decided that this is a valuable property - but the production of tubes is becoming relatively more expensive as demand for them diminishes and they require specialty, limited-run manufacturing (compared to transistors, demand for which is growing).   In all, thinking from your practical needs before jump into any conclusion, whether tube amplifier is worth it or not, there’s no absolute answer to this question. VIII. How to Extend the Life of the Tube Amplifier?    The problem of short life of the tube amplifier is often criticized, but this is often not a problem of the tube amplifier itself, but a defect in the circuit design and a problem in use. It should be noted that a good quality tube amplifier must have a correctly designed circuit, sufficient heat dissipation, and thoughtful shock absorption.   In use, the tube amplifier must have good ventilation and heat dissipation. Overheating of the temperature will inevitably shorten the life of the tube, so the tube amplifier should be kept as low as possible.   Vibration is not good for tube amplifiers, so it is important to take anti-vibration measures to avoid vibration as much as possible. If these two can be achieved, the service life of the tube amplifier can be at least doubled. For this reason, there should be a proper space around the tube amplifier equipment, especially above it, in order to have good convection ventilation, if possible, a fan can be used to help dissipate heat.   When the cathode of the tube amplifier has not reached the required temperature, the high-voltage power supply is immediately applied, and its cathode will be damaged, which will also shorten the life of the tube amplifier.   Therefore, if the tube amplifier equipment has a preheating device, it must be used. For example, first turn on the filament low-voltage power supply to preheat, and then turn on the high-voltage power supply. If there is no preheating device, don't rush to connect the input signal, you can turn the volume down to the minimum, wait for 20-30 minutes to warm up the machine before using it.   If the indirectly heated rectifier tube is used to supply the high voltage of the whole machine, it just provides a simple and effective high voltage delay. In addition, do not switch the power supply frequently during normal use.   Of course, if the tube amplifier circuit is designed correctly and the wrong use is avoided, the tube amplifier will not "die young". It should be normal for the tube amplifier to use thousands of listening hours.   The most common mistakes in circuit design are: 1. The potential difference between the filament and the cathode of the tube amplifier is too high 2. The screen or screen grid voltage of the tube amplifier is applied to the maximum value 3. The filament voltage of the tube amplifier is too low or too high 4. Improper installation position of the tube amplifier causes the electrode to overheat and the high-voltage power supply does not have a delay device, etc.   Therefore, these problems should be avoided when designing the circuit to effectively extend the service life of the tube amplifier. FAQ 1. Why is a tube amp better? Tubes, like analog recordings, have a more full-bodied sound than transistor gear. There's a "roundness" to tube sound that solid-state gear never equals. Tubes are less forgiving about mismatches, so to get the best out of a tube amp it must be used with just the right speaker. 2. What is tube amplifier used for? Tube amplifiers, or tube amps as they're commonly called, are tiny electronic or electromagnetic components that are used to boost electric current in devices to improve their performance. It's what makes your hearing aid pick up sounds through a microphone from all around you. 3. Are tube amps worth it? In many cases, tube amps do not require the amount of maintenance that they have a reputation for. As long as you properly take care of your gear, owning a tube amp is simple and very well worth it for the tone. 4. How long should a tube amp warm up? 20 to 30 minutes. As a rule of thumb, your tube amp needs to be warmed up for 20 to 30 minutes at least before you can start playing your guitar. 5. Why are tube amps louder? When tubes are driven outside their linear region, for the first 12db or so of overdrive the harmonics that they produce trick the human ear into thinking that the sounds are getting louder, when in fact the sound is getting progressively more distorted. 6. How does a tube amplifier work? The power transformer and rectifier work together as an electron pump which pulls electrons out of the amp circuit creating a positive voltage (electron scarcity = positive voltage). The amplifier's electronics need DC to amplify. The amp is powered by DC but the guitar signal moving through the amp is AC. 7. What's the difference between a tube amp and a regular amp? The physical difference between a solid-state amp and a tube amp is that a solid-state machine derives amplification from electronic transistors, while a tube amp uses vacuum tubes (also known as valves). ... Solid-state amps are great for players who want maximum headroom (a.k.a a loud, clean, undistorted signal). 8. Which is better tube amp or solid state? Tube amps are generally more expensive in initial cost and to operate (because you need to replace the tubes occasionally), and solid-state amps are generally less delicate and more reliable. Many players, however, feel that tube amps yield a warmer, more musical tone and more musical-sounding distortion. 9. How often should a tube amp be serviced? 15 years. If its a well made amp, recap every 10 or 15 years, retube as needed. Fenders might go many years without needed a power tube replaced. 10. How many watts do I need in a tube amp? 100 watts. You'll need a solid state amp that has around 100 watts, or a valve amp that has around 50 watts. This will usually give you enough volume that you can be heard over the drummer, without having to push your amp's volume too hard so that the distortion becomes overbearing.

IntroductionThe operational amplifier is an integrated circuit that has two input pins and one output pin. It is used to amplify and output the voltage difference between the two input pins. Based on its characteristics, operational amplifier has different functions in different circuits. Here introduces common and fundamental op amp circuits examples with descriptions.A Basic Introduction to Op Amp CircuitsCatalogIntroductionOp Amp Diagram and Circuit Analysis1.1 What is the Inverting & Non-inverting Amplifier?1.2 Differential Amplifier1.3 Summing Amplifier1.4 Practical Differentiator1.5 Op-amp Integrator1.6 Converter, Detector, Bias Current Compensation, Voltage Comparator1.7 Offset Voltage Adjustment1.8 Sine Wave Generator1.9 Op-Amp Voltage Reference1.10 Instrumentation Amplifier1.11 Precision Current Sink & Source1.12 Precision Diode & Clamp1.13 Notch Filter Amplifier1.14 Capacitance Multiplier2 Other Op-amp Circuit ApplicationsOp Amp Diagram and Circuit AnalysisHow do you build an op amp circuit? This part introduces the most basic operational amplifier circuits. Understand the role of op amp in different circuits, and do reference design for your own amplifier circuit through the description of the op amp equations. What’s more, you can handle the most common op amp applications through these circuits.1.1 What is the Inverting & Non-inverting Amplifier?Figure 1. Inverting AmplifierIn an inverting amplifier circuit, the operational amplifier inverting input receives feedback from the output of the amplifier. Assuming the op-amp is ideal and applying the concept of virtual short at the input terminals of op-amp, the voltage at the inverting terminal is equal to non-inverting terminal. Figure 2. Inverting Amplifier with High Input ImpedanceIn electronics, high impedance means that a point in a circuit (a node) allows a relatively small amount of current through. For an inverting amplifier, the input impedance is approximately equal to the input resistance. This is because the input resistor is connected to “virtual ground” in the inverting configuration.Another Example:Figure 3. Fast Inverting Amplifier with High Input Impedance Figure 4. Non-inverting AmplifierA non-inverting amplifier is an op-amp circuit configuration which produces an amplified output signal. This output signal of non-inverting op amp is in-phase with the input signal applied. In other words a non-inverting amplifier behaves like a voltage follower circuit.Another Example:Figure 5. Non-inverting AC AmplifierRecommended Readings: Inverting and Non-inverting Amplifier and Their Basics......(1)Op Amp High Input Impedance and Low Output Impedance......(2)1.2 Differential AmplifierFigure 6.The differential amplifier circuit is a very useful op-amp circuit and by adding more resistors in parallel with the input resistors. It usually has two outputs and two inputs, which is a special purpose amplifier designed to measure differential signals, otherwise known as a subtractor. 1.3 Summing AmplifierThe Summing Amplifier is another type of operational amplifier circuit configuration that is used to combine the voltages present on two or more inputs into a single output voltage.Example Explained:Figure 7. Fast Summing Amplifier with Low Input Current Figure 8. Inverting Summing AmplifierThe inverting summing amplifier is another type of operational amplifier circuit configuration that is used to combine the voltages present on two or more inputs into a single output voltage. When the summing point is connected to the inverting input of the op-amp the circuit will produce the negative sum of any number of input voltages. Figure 9. Non-inverting Summing AmplifierThe non-inverting summing amplifier is a similar configuration to the inverting summing amplifier. In other words, it is based around the configuration of a non-inverting operational amplifier circuit in that the input (either ac or dc) is applied to the non-inverting (+) terminal, while the required negative feedback and gain is achieved by feeding back some portion. 1.4 Practical DifferentiatorFigure 11.A practical differentiator amplifier is basically a high pass filter and are used in wave shaping circuits, frequency modulators etc. Because differentiators have frequency limitations while operating on sine wave inputs; the circuit attenuates all low frequency signal components and allows only high frequency components at the output. In other words, the circuit behaves like a high-pass filter. 1.5 Op-amp IntegratorAn op-amp integrator is an electronic integration circuit that performs the mathematical operation of Integration, that is we can cause the output to respond to changes in the input voltage over time as the op-amp integrator produces an output voltage which is proportional to the integral.Figure 12. Fast Integrator Figure 13. Fast Integrator with Low Input Current Figure 14. Low Drift IntergratorIn Low Drift Intergrator circuit, the output of an operational amplifier always contains signals that could not have been predicted, even with knowledge of the input and an accurately. 1.6 Converter, Detector, Bias Current Compensation, Voltage ComparatorFigure 15. Current to Volatge ConverterA current to voltage converter will produce a voltage proportional to the applied input current. This circuit is required if your measuring instrument is capable only of measuring voltages and you need to measure the current output. Figure 16. Precision AC to DC ConverterA simple full wave precision rectifier using a single supply operational amplifier in saturation mode, which is to insure precision half wave rectification and unidirectional current flow. Figure 17. Temperature Compensated Logarithmic ConverterA temperature compensated logarithmic amplifier for signal strength indicator or automatic gain control applications is presented.  Figure 18. Double-Ended Limit DetectorThe circuit in see a differential Input to single ended output amplifier will convert a differential (double ended) signal. Figure 19. Fast Zero Crossing DetectorA zero-crossing detector whose input is a sign wave has been converted into a train of positive pulses at interval T by adding a RC network and a clipping. It can be used to detect phase anomalies, or even as a 'loss of AC' detector, purposes of synchronization, fast and accurate frequency. Figure 20. Low Drift Peak DetectorOp-amp based peak detector circuit is the modification of basic peak detector circuit, used to remove the voltage drop across the diode. It stores the peak value of input voltages for infinite time duration until it comes to reset condition. Figure 21. Op Amp Integrator with Bias Current CompensationThe operational amplifier integrator is an electronic integration circuit, where the resistor producing a compensating current flow through the series capacitor to maintain the virtual ground. Figure 22. Voltage Comparator for Driving DTL or TTL Integrated CircuitHigh frequency performance at any gain as a comparator the output can be drived DTL or TTL integrated circuit. Figure 23. Threshed Detector for PhotodiodesUse operational amplifiers or op-amps to convert the photodiode current to a measurable voltage. 1.7 Offset Voltage AdjustmentThe input offset voltage is defined as the voltage that must be applied between the two input terminals of the op amp to obtain zero volts at the output. Ideally the output of the op amp should be at zero volts when the inputs are grounded. The presence of offset can be encapsulated by assuming that the real Op Amp input/output transfer characteristic is y = A (V + – V – + e ) where e is the error in the differential input to the ideal Op Amp.Figure 24. Offset Voltage Adjustment for Inverting Amplifiers Using Any Type of Feedback Element Figure 25. Offset Voltage Adjustment for Non-inverting Amplifiers Using Any Type of Feedback Element Figure 26. Offset Voltage Adjustment for Voltage Followers Figure 27. Offset Voltage Adjustment for Differential Amplifiers Figure 28. Offset Voltage Adjustment for Inverting Amplifiers Using 10kΩ Source Resistance or Less 1.8 Sine Wave GeneratorSine Wave Generator Using Op AmpThe Sine Wave Generator is a type of electronic equipment that generates an oscillating frequency in a sinusoidal pattern. One of the popular methods of generating a sine wave with an operational amplifier is to use the Wien bridge configuration.Figure 29. Low Frequency Sine Wave Generator with Quadrature Output Figure 30. High Frequency Sine Wave Generator with Quadrature Output 1.9 Op-Amp Voltage ReferenceA voltage reference, or a VREF, is a precision device designed to maintain an accurate, low noise, constant output voltage. Ideally, the output should remain constant even as parameters, such as ambient temperature, supply voltage, or the load current change.Figure 31. Positive Voltage ReferenceIn a positive voltage reference a non-inverting op-amp buffer is often included to scale the output voltage and supply any current needed. Figure 32. Negative Voltage ReferenceA common way to generate a negative voltage has been to use an operational amplifier (op amp) to invert the output of a positive precision voltage reference. This approach typically requires a positive reference, the op amp, and two supply rails to generate the negative output. 1.10 Instrumentation AmplifierInstrumentation amplifier is a kind of differential amplifier with additional input buffer stages. It is a differential op-amp circuit providing high input impedance with ease of gain adjustment. Basically, a typical Instrumentation Amplifier configuration consists of three Op-amps and several resistors.Figure 33. Differential-input Instrumentation Amplifier Figure 34. Variable Gain, Differential-input Instrumentation Amplifier Figure 35. Instrumentation Amplifier with ±100V Common Mode Range Figure 36. Instrumentation Amplifier with ±10V Common Mode Range Figure 37. High Input Impedance Instrumentation Amplifier 1.11 Precision Current Sink & SourceOp Amp can source or sink current.Sourcing current means that current is flowing out of the op-amp into the load. Sinking current means that current is flowing in to the op-amp.Figure 38. Precision Current SinkFor a current sink circuit, opamp are designed to be used in both positive and negative voltages. The op-amp connection is changed, that is the negative input is connected to a shunt resistor. Figure 39. Precision Current SourcePrecision current sources have traditionally been built using op amps, resistors, and other discrete components—with limitations due to size, accuracy. Figure 40. Bilateral Current Source 1.12 Precision Diode & ClampFigure 41. Precision DiodeIn this circuit , the op-amp circuit is required to work as an ideal diode. That is, an ideal op-amp wants to make its two inputs equal in voltage through the negative feedback path. Figure 42. Precision ClampPrecision Op-Amp Clamp Circuit is the same circuit as the classic simple precision rectifier (set to pass the negative half-sine), but with the non-inverting input of the op-amp. 1.13 Notch Filter AmplifierNotch filter is a useful circuit to suppress middle- and high-frequency resonance to improve control precision. It work on only a narrow band of frequencies. To be useful, the notch filter must be tuned to the frequency of resonance or of noise generation.Figure 43. Adjustable Q Notch Filter Figure 44. Easily Tuned Notch Filter 1.14 Capacitance MultiplierCapacitance Multiplier uses an op-amp and a small capacitor to simulate a much larger capacitor instead of a transistor.Example Explained:Figure 45. Negative Capacitance Multiplier Figure 46. Variable Capacitance Multiplier Figure 47. Analog MultiplierIn electronics, an analog multiplier is a device which takes two analog signals and produces an output which is their product. Analog multipliers take two or more analog signals and produce an output which is their product or the sum of multiple products. 2 Other Op-amp Circuit DesignFigure 48. Free-Running MultivibratorThe Op-amp Multivibrator is an astable oscillator circuit that generates a rectangular output waveform using an RC timing network connected to the inverting end. An astable multivibrator uses an op-amp. It generates square waves of its own i.e. without any external excitation. Figure 49. Op Amp Function GeneratorFunction generator system can be readily synthesized using operational amplifiers on an approach which uses full when the need for a special need. Figure 50. Pulse-width Modulator (PWM)Pulse-width Modulator is a way to control analog devices with a digital output. It uses digital signals to control power applications, as well as being fairly easy to convert back to analog with a minimum of signal. High-frequency op amps can be used for a high-frequency PWM, because op amps are used for the modulator. Bridge AmplifierThe bridge amplifier is to generate both an inverted and a noninverted output signal. When the amplifier is switched into bridge-mode operation, the signal at the output of the first stage of amplification of channel A is attenuated. In addition, bridging an amplifier refers to the process of combining two of four channels into one or two channels with half the ohms.Figure 51. Bridge Amplifier with Low Noise Compensation Figure 52. Wien Bridge Sine Wave OscillatorA Wien bridge oscillator is a simple circuit that can be set to continuous oscillation, which outputs a sine wave. It acts as a useful reference oscillator for analog circuits, and the output signal can then be manipulated with other analog circuits. It is an excellent circuit for generating a sine wave signal at audio frequencies. Figure 53. Low Power Supply for Intergrated Circuit TestingOp-amp IC Testing Circuit basically has voltage comparator inside, which has two inputs, one is inverting input and second is non-inverting input. In normal, putting a good op-amp into the circuit, and they will generate a low frequency in the square wave. Figure 54. Fast Half Wave RectifierPrecision half-wave rectifiers are commonly used with other op amp circuits such as a peak-detector or bandwidth limited non-inverting amplifier to produce a DC output voltage. For the positive half cycle of the sinusoidal input, the output of the op-amp will be negative. Figure 55. Absolute Value Amplifier with Polarity DetectorAbsolute Value Amplifier with Polarity Detector Circuit breaks an input voltage signal down into its components. It will handle direct input voltages as well as alternating voltages up to several kHz. Figure 56. Sample and Hold Circuit Using Op AmpIn electronics, a sample and hold (also known as sample and follow) circuit is an analog device that samples (captures, takes) the voltage of a continuously varying analog signal and holds (locks, freezes) its value at a constant level for a specified minimum period of time. It consists of switching devices, capacitor and an operational amplifier. Figure 57. Tuned CircuitA tuned circuit has a very high impedance at its resonant frequency (ideally = infinity). At other frequencies, its impedance is lower. Tuned circuits are used to select or tune in radio stations on a particular frequency and reject all the others. When an amplifier circuit has its load replaced by a tuned circuit, such an amplifier can be called as a tuned amplifier circuit. It is generally referred to as active filters.Another Example:Figure 58. Two-Stage Tuned Circuit Figure 59. Simulated InductorA simulated inductor is an active circuit for generating an equivalent inductive reactance, which is implemented with active and passive components. It is used in the design of filters, amplifiers, oscillators and tuned amplifiers. Figure 60. High Pass Active FilterA high-pass filter (HPF) is an electronic filter that passes signals with a frequency higher than a certain cutoff frequency and attenuates signals with low frequencies. Active High Pass Filter uses inverting operational amplifier with high voltage gain. Figure 61. Low Pass Active FilterA simple active low pass filter is formed by using an op-amp. The operational amplifier will take the high impedance signal as input and gives a low impedance signal as output. The circuit uses an op-amp for amplification and gain control. Figure 62. Nonlinear OP AMP with Temperature Compensated BreakpointsAs long as the gain of the operational amplifier is large enough, the amplification of the circuit is determined by the external feedback resistance network. Figure 63. Current MonitorA current monitor amplifier is a special purpose integrated circuit differential amplifier that is designed to sense the voltage developed across a current shunt and output a voltage proportional to the measured current. Figure 64. Power Booster AmplifierA power booster amplifier is typically a hybrid circuit with thick film resistors, ceramic capacitors. A novel power booster amplifier is based on a modified half-bridge topology using separated switches and a floating bridge capacitor. Figure 65. Long Interval TimerWith the help of high gain high impedance operational amplifier, we can build a long time delay with resistor-capacitor (RC) circuit. Figure 66. Amplifier for Piezoelectric TransducerThe charge sensitive amplifiers employed for piezo electric sensors cover quite wide range. Piezoelectric transducers used as sensors, typically, the high impedance of the sensor requires an amplifier. Figure 67. Temperature ProbeAn inverting op amp operates with a noise gain of two, which produces twice as much output offset voltage as does a unity-gain buffer. This is a fantastic solution to temperature monitoring. Figure 68. Photodiode AmplifierPhotodiode amplifier circuit pedance amplifier for amplifying the light- dependent current of a photodiode. The high gain of the op-amp keeps the photodiode current equal to the feedback current. Some are ideally suited for ultra low noise amplification of very small photodiode currents. Figure 69. High Input Impedance AC FollowerOperational amplifiers have a very high input impedance, which means that they don't suck in much current (ideally, none) at the inputs, typically above 1MΩ as it is equal to that of the operational amplifiers input resistance. Low output impedance and extremely high input impedance make it a simple and effective solution to problematic impedance. Figure 70. Root ExtractorThe proposed extractor is based on the use of two operational amplifiers (op amps) as only active elements. Figure 71. Basic Log AmplifierA logarithmic amplifier, or a log amplifier, is an electronic circuit that produces an output that is proportional to the logarithm of the applied input. The simple logarithmic amplifier uses a junction diode as a nonlinear element. In addition, the basic log amplifier can also be constructed by replacing diode by a transistor. The output is proportional to the logarithm of the input given by. Figure 72. Circuit for Operating the LM101 without a Negative Supply Figure 73. Circuit for Generating the Second Positive Voltage Figure 74. Multiple Aperture Window Discriminator Figure 75. Neutralizing Input Capacitance to Optimize Response Time Figure 76. Saturating Serve Preamplifier with Rate FeedbackFrequently Asked Questions about Op Amp Circuits1. What is an op amp circuit?An operational amplifier is an integrated circuit that can amplify weak electric signals. An operational amplifier has two input pins and one output pin. Its basic role is to amplify and output the voltage difference between the two input pins. 2. Why use an op amp in a circuit?To convert the current into voltage, a simple circuit with an operational amplifier, a feedback loop through a resistor on the non-inverting, and the diode connected between the two input pins allows you to get an output voltage proportional to current generated by the photodiode, which is evident by the light. 3. How do op amp circuits work?An operational amplifier, or op amp, generally comprises a differential-input stage with high input impedance, an intermediate-gain stage, and a push-pull output stage with a low output impedance. ... That is, the output gets fed back to the inverting input through some impedance. 4. What are the advantages of op amps circuit?An op-amp circuit buffers the sensor and allows gain or attenuation circuits to be developed. The output of the sensor is non-linear. An inverting op amp circuit gives you a more linear output than a non-inverting op-amp circuit does. 5. What are the ideal characteristics of op amp?The so-called ideal op amp is to idealize various technical indicators of op amps, and it must have the following characteristics.1) Infinite Input Resistance2) Zero Output Impedance3) Infinite Open-loop Gain4) Infinite Common-mode Rejection Ratio5) Infinite Bandwidth