It combines • Precise 1 dB Gain Steps precision gain control with a low noise, ultra-linear, © 2004-2021 FreePatentsOnline.com. Analog Devices voltage controlled variable gain amplifiers (VGAs) provide continuous gain control over a wide dynamic range for a variety of audio and optical frequency bands. Variable gain op amp circuit. The −3-dB bandwidth is 900 MHz at all gains. Voltage Controlled Variable Gain Amplifier. Fig. In today’s electronics, you might be wonder how such circuit can be useful in this digital domination era. We use cookies to ensure that we give you the best experience on our website. The Howland current pump. An amplifier that is said to have a gain of 20 dB might have a voltage gain of 20 dB and an available power gain of much more than 20 dB (power ratio of 100)—yet actually deliver a much lower power gain if, for example, the input is from a 600 Ω microphone and the output connects to a 47 kΩ input socket for a power amplifier. The tee attenuator provides for optimum dynamic linear range attenuation up to … If you continue to use this site we will assume that you are happy with it. For you those are not familiar with analog circuits, it might seem difficult to find a practical  application of analog video amplifier circuit. a gain control voltage/current conversion circuit (3) converting a gain control voltage into a gain control current varying linearly against the gain control voltage; and U1897E FET can also be replaced with a 2N4091. 11 is a circuit diagram showing a second example circuit (in which the cascode connection is not used) of the reference current generation circuit constituting the voltage controlled variable gain amplifier circuit according to the embodiment of this invention. operational-amplifier gain unity-gain. In electronics, gain is a measure of the ability of a two-port circuit (often an amplifier) to increase the power or amplitude of a signal from the input to the output port by adding energy converted from some power supply to the signal. A two-stage VGA was fabricated in a 0.35 μ m CMOS … Gain accuracy at each setting is typically 0.1 dB. Now you can find various micro controller with high speed ADC, and you would probably need this circuit  for signal conditioner, making all RGB lines conversion uses the full range of the ADC. The proposed circuit is composed of two transimpedance amplifiers and a transconductance amplifier. 10 or Fig. The proposed circuit merges a source-degenerated transconductance amplifier with a current-mode transimpedance amplifier, which renders voltage gain control with constant bandwidth. Thus by inserting an audio signal (±10 mV) within pin 2 and 3 and with controlling the current on pin 5, the amount of the signal output (pin 6) is controlled. 1. The LMH6518 device is a digitally controlled variable gain amplifier whose total gain is varied from −1.16 dB to 38.8 dB for a 40 dB range in 2-dB steps. 4A and 4B are circuit diagrams showing a current bypass circuit constituting the voltage controlled variable gain amplifier circuit according to the embodiment of this invention. The circuit diagram of a typical Cascode amplifier using FET is shown above. For you those are not familiar with analog circuits, it might seem difficult to find a practical application of analog video amplifier circuit. A current ILsc is inserted into this input which controls the gain of the device linerly. The drain-to-source voltage of the JFET is labeled vAin the figure. The input signal (green) is a 20khz sine wave of a fixed amplitude. This has consumed me for the past month. This is a video amplifier circuit featured with controllable variable gain. The basic circuit is shown in Figure 1. It can amplify the signal voltage amplitude well. The constant gm type reference current generation circuit 4 is suitable for using in the voltage controlled variable gain amplifier circuit 100 as described above, and may be used in a two-stage amplifier circuit 100A as shown in Fig. TABLE 1: OVERVIEW OF GAIN RANGES FOR EXAMPLE CIRCUITS(1,2) Op Amp (1) VIN VOUT AB W + – Pot1 R 1 R 2 Inverting Amplifier Circuit (a) C FC (2) Op Amp VIN B + 1 Non-Inverting Amplifier Circuit (b) Note 1: A general purpose op amp, such as the MCP6001. The voltage controlled variable gain amplifier circuit varies its gain linearly and continuously against the gain control voltage, as described above. Figure 1 shows the practical circuit of an inverting DC amplifier with an overall voltage gain (A) of x10 (= 20dB), and with an offset nulling facility that enables the output to be set to precisely zero with zero applied input. The first differential amplifier and the second differential amplifier are connected in series. The circuit uses a single operational amplifier, two resistors and a variable resistor. It comes in a tiny, low profile package (5x5x0.89mm), accommodating dense circuit board layouts. A variable gain setting resistance circuit having a variable resistance is the gain setting resistor positioned between the op amp's inverting input and a low voltage supply. Fig. Op-Amp with Voltage Controlled Gain and Unity DC Gain. … A variable gain setting resistance circuit having a variable resistance is the gain setting resistor positioned between the op amp's inverting input and a low voltage supply. Fig. & Terms of Use. A, AD603 chip introduction. The variable gain element in the VCA is a JFET operated in its linear or triode region. The above image is a single operational amplifier. This circuit still give a linear attenuation even at f=10.7MHz. Targeted for IF signal chain Fig. Furthermore, a rudimentary example of a variable gain amplifier is your typical inverting operational amplifier configuration with an LDR (light dependent resistor) in its feedback loop. 10 or Fig. 10 is a circuit diagram showing a first example circuit (in which cascode connection is used) of a reference current generation circuit constituting the voltage controlled variable gain amplifier circuit according to the embodiment of this invention. In signal condition domain, a critical functional block is a VGA or Variable Gain Amplifier. Fig. The VGA control is ensured by using a voltage-controlled active resistor VG. Fig. It provides accurate pin selectable gains from −11 dB to +31 dB at 90 MHz bandwidth and +9 dB to +51 dB at 9 MHz bandwidth. How to make this two synchronized voltages is described as follow: the first FET is fed with U1, which ranges from 0 to -10 V, and the second FET is controlled by U2, which is synchronized as (-10 – U1) V.  This control voltages can be obtained from DAC (digital-to-analog converter) or a stereo potentiometer (as depicted in the diagram). Voltage follower amplifier U1A buffers Q1A’s drain terminal’s voltage controlled attenuated signal. Technically, they are usually current-controlled, but when you put a current through an element like a resistor you convert a current to a voltage. Glawe, Delfs, Moll (Rothenbaumchaussee 58, DE). 2 is a circuit diagram of a first differential amplifier constituting the voltage controlled variable gain amplifier circuit according to the embodiment of this invention. The output stage is an FET common gate amplifier which is driven by the input stage. Just as an example a Differential Amplifier amplifies the voltage difference present on its inputs both inverting and non-inverting which is what I think you are getting at. If you prefer to use operational amplifiers, the Howland current pump produces a voltage-controlled current and requires only one op-amp and four resistors. IV LM324 AC Signal Three Distribution Amplifier Circuit. Abstract— A novel current-mode CMOS digitally controlled variable gain amplifier (VGA) is presented in this paper. An example is a volume control dial. Also, variable gain amplifiers are in use in various applications, including synthesizers, amplitude modulation, and audio level compression. The circuit simply uses a single variable gain amplifier. The control voltage input typically may be tuned so that the Size: 50mm * 39mm Supply voltage range:±5v Highlights This amplifier module is a voltage controllable gain amplifier. Op-amp or Operational Amplifier is the backbone of Analog Electronics and is used in many applications, such as Summing Amplifier, differential amplifier, Instrumentation Amplifier, Op-Amp Integrator, etc. A simple VGA consists of a few resistors with different values, an operational amplifier and components that switch between these resistors. In such a case, a single power supply is sufficient. A two-stage VGA was fabricated in a 0.35 μ m CMOS … Voltage controlled variable gain amplifier circuit. Applications include audio level compression, synthesizers and amplitude modulation. Voltage amplifiers, many times, are built with op amp circuits. where A o is the low frequency open-loop voltage gain of the op-amp (typically 100dB, or x100,000, e 1 is the signal voltage at the non-inverting input terminal, and e 2 is the signal voltage at the inverting input terminal). & Terms of Use. FIGURE 1: Amplifier with Programmable Gain Example Circuits. Fig. The voltage gain and input impedance are determined by the R1 and R2 values, and can be altered to suit individual needs. February 2, 2010 Circuitguy. In addition, the power supply voltage dependence of the voltage controlled variable gain amplifier circuit is suppressed. The dB-linear gain is controlled linearly by the gate voltage, resulting in a simple and robust VGA. A voltage-controlled amplifier or variable gain amplifier is an electronic device (amplifier) that varies its gain depending on the applied control voltage (CV). The input stage of the circuit is an FET common source amplifier and the input voltage (Vin) is applied to its gate. Free electronic circuit design and schematic diagram. Abstract: This paper describes use of a novel exponential approximation for designing dB-linear variable gain amplifiers (VGAs). In this configuration, the input voltage signal, ( VIN ) is applied directly to the non-inverting ( + ) input terminal which means that the output gain of the amplifier becomes Positive in value in contrast to the Inverting Amplifier circuit we saw in the last tutorial whose output gain is negative in value. Fig. This circuit can generate dynamic linear range attenuation up to 100 dB. Thank you in advance. This is Variable Gain Amplifier controlled by voltage circuit function as video amplifier, it use 3 Field Effect Transistor (FET) type U1897E. Advantages of the JFET as a VCR are that: 1. Design and Testing of Voltage Controlled Variable Gain Amplifier Using Differential Amplifier For example, you have a VGA output only on your old device, but the whole new system accept only USB interface or other digital interface. To understand the working of this circuit it is essential to know how an operational amplifier works. 5 shows a correlation between a gain control current and a gain control voltage. This type of circuit has many applications, including audio level compression, synthesizers and amplitude modulation. 11. A non-attenuating automatic variable gain amplifier (VGA) circuit includes an operational amplifier (op amp) with a feedback resistor connected between its output and inverting input terminals. Ask Question Asked 4 years, 4 months ago. Note that FET input op amps such as TL082, TL062, LF353, AD712, etc. A variable-gain or voltage-controlled amplifier is an electronic amplifier that varies its gain depending on a control voltage (often abbreviated CV). 1 is a block diagram showing a voltage controlled variable gain amplifier circuit according to an embodiment of this invention. The circuit uses a single operational amplifier, two resistors and a variable resistor. The VCA810 is a DC-coupled, wideband, continuously variable, voltage-controlled gain amplifier. The Voltage controlled variable gain amplifier circuit is built with ic op amp type LM101. 12 is a block diagram of a two-stage amplifier circuit using the reference current generation circuit shown in Fig. The proposed circuit merges a source-degenerated transconductance amplifier with a current-mode transimpedance amplifier, which renders voltage gain control with constant bandwidth. Vbias, which is shown as a variable DC negative voltage varies Q1A’s drain to source resistance to provide a voltage controlled voltage divider circuit via series resistor R2. The gain tuning is achieved by using an active resistor. This circuit can generate dynamic linear range attenuation up to 100 dB. The object of this experiment is to assemble and test a voltage controlled ampli fier (VCA) that might be used as a variable gain stage in a compressor, a limiter, or a guitar e ffects box. Figs. That is, as understood from Equation 34, the variations due to the semiconductor manufacturing processes and the temperature dependence of the gain G1 of the first differential amplifier 1 can be suppressed as well. 13 is a block diagram of a single-stage amplifier circuit using the reference current generation circuit shown in Fig. 13 as well. In this paper, a voltage mode variable gain amplifier (VGA) is presented. Coarse gain tuning is achieved by using a switched-resistor network, while fine gain tuning is obtained by using a voltage-controlled active resistor. The voltage controlled variable gain amplifier circuit includes a first differential amplifier, a second differential amplifier, a gain control voltage/current conversion circuit and a reference current generation circuit. But in some situation, there will be a need to interface old (legacy) into a new system, and that’s the reason why this very basic circuit is needed. In order to make it useful, you still have to supply the control signal with signals which allow the voltage gain to change over time. 6 shows a correlation between a gain of the voltage controlled variable gain amplifier and the gain control voltage. nominal level. Privacy Policy AD603 Introduction . Functionally, the gain of the a… Also, variable gain amplifiers are in use in various applications, including synthesizers, amplitude modulation, and audio level compression. The voltage controlled variable gain amplifier circuit includes a first differential amplifier, a second differential amplifier, a gain control voltage/current conversion circuit and a reference current generation circuit. Like it’s name suggests, it is an amplifier whose amplification, or gain, is controlled by a voltage. Rd is the drain resistance of the output stage. If we look closely in the above image, there … Analog Devices voltage controlled variable gain amplifiers (VGAs) provide continuous gain control over a wide dynamic range for a variety of audio and optical frequency bands. Then using the formula to calculate the output voltage of a potential divide… a current bypass circuit (50) forming bypass routes through each of which a portion of the reference current corresponding to the gain control current bypasses a corresponding differential input transistor (11,12). This invention provides a voltage controlled variable gain amplifier circuit that varies its gain linearly and continuously against a gain control voltage VC. The gain control circuit is especially suitable for volume expansion applications. Additionally not only is the gain varied but also the sign. Model an op amp with a dependent source. Fig. The control is done by adjusting the voltage of grid inputs of two FETs, which are configured as programmable voltage divider. It provides accurate, pin-selectable gains of −11 dB to +31 dB with a bandwidth of 90 MHz or +9 dB to 51+ dB with a bandwidth of 9 MHz. The control is done by adjusting the voltage of grid inputs of two FETs, which are configured as programmable voltage divider. Additionally not only is the gain varied but also the sign. AD603 Video gain control voltage controlled variable gain amplifier circuit subwoofer amplifier . The AD603 is a low noise, voltage-controlled amplifier for use in RF and IF AGC systems. 8 shows power supply voltage dependence of the gain in the case of the first example circuit of the gain control voltage/current conversion circuit. Variable gain amplifiers deliver unmatched performance for signal chains that require high dynamic range. You can see a grounded 0.001 uF capacitor  to filter the control voltage from any glitch caused by dirty or bad potentiometer. A variable-gain or voltage-controlled amplifier is an electronic amplifier that varies its gain depending on a control voltage (often abbreviated CV). The voltage input on the left is varied to adjust the … Furthermore, the variations due to semiconductor manufacturing processes and temperature dependence of the gain of the voltage controlled variable gain amplifier circuit can be also suppressed. General. However, this control voltage can be given from a variable voltage divider using any kind of potentiometer. It is composed of two AD603 cascade amplifiers. open-in-new Find other Programmable & variable gain amplifiers (PGA/VGA) Description. The exponential function is accurately generated using a simple error-compensation technique. A non-attenuating automatic variable gain amplifier (VGA) circuit includes an operational amplifier (op amp) with a feedback resistor connected between its output and inverting input terminals. Figs. maximum gain and unity gain bandwidth of the op amp used. You can see the control is done by a potentiometer, but you can replace with any voltage source ranging from zero to -10V, just make sure each of the two FETs is fed with different synchronized voltages. However, when the analog signal path is digitally controlled, a digital potentiometer might be used to control gain. Things that can force changes to this circuit are many, but are mostly limited to larger and smaller input signals and higher or lower supply voltage ranges. This circuit still give a linear attenuation even at f=10.7MHz. The first differential amplifier and the second differential amplifier are connected in series. A fully differential implementation is used to suppress the common mode noise and increase the dynamic range. February 5, 2013 Rend. a first differential amplifier (1) and a second differential amplifier (2), each comprising a constant current source (13) generating a reference current , a pair of differential input transistors (11,12) to which the reference current from the constant current source is supplied, a pair of output terminals (24,25) outputting a pair of differential output voltages, and first and second output resistors (22,23) connected in series between the pair of output terminals (24,25), the second differential amplifier (2) receiving the pair of differential output voltages of the first differential amplifier (1); Variable Gain Amplifiers (VGA) Variable gain amplifiers (VGAs) are used in a variety of remote sensing and communications equipment. The 2N5457 works as a voltage variable resistor having an Rds (on) max of 800 ohms. A voltage-controlled amplifier or variable gain amplifier is an electronic device (amplifier) that varies its gain depending on the applied control voltage (CV). The voltage gain A for an op amp is very large ... All op amp circuits shown here operate in the linear active region. Our VGAs improve the dynamic range of a circuit by allowing users to adjust a signal’s amplitude in real time, which is invaluable for ultrasound, speech analysis, radar, wir Privacy Policy Using this circuit the gain can be calculated from the formula given above. Then, the gain G1 is represented by Equation 33: G⁢1=μp⋅Cox⋅S⁢1⋅IRO⋅RO, Equation 34 is obtained by substituting IRO represented by Equations 32 into Equation 33: G⁢1=2⁢S⁢1S⁢4⋅1-1K⋅RORB, The total gain G of the voltage controlled variable gain amplifier circuit 100 is derived from Equation 9 and represented by Equation 35: G=G⁢1×G⁢2=2⁢S⁢1S⁢4⋅1-1K2⋅RORB2=γ⋅RORB2, γ in Equation 35 is represented by Equation 36: γ=2⁢S⁢1S⁢4⋅1-1K2. Works as a voltage variable resistor is in-phase with the input stage of JFET... Proper layout controlled gain or filter blocks a higher voltage differential implementation used... The tee attenuator provides for optimum dynamic linear range attenuation up to 100 dB in Fig expansion applications it. Are not familiar with analog circuits, it might seem difficult to Find a practical application analog! With the input signal addition, the power supply voltage dependence of the second circuit. Input op amps such as TL082, TL062, LF353, AD712, etc bandwidth of the potentiometer... Mode noise and increase the dynamic range in-phase with the input signal green! Glawe, Delfs, Moll ( Rothenbaumchaussee 58, DE ), two resistors and a gain control current requires... Circuit according to an embodiment of this is a low power, wideband, DC-coupled voltage-controlled! That switch between these resistors shown in Fig these resistors and input impedance are determined by the voltage... S voltage controlled variable gain amplifier circuit using the reference current generation circuit shown Fig! Db resolution 4 years, 4 months ago block diagram showing a voltage amplifier with a.! The sign 12 voltage controlled variable gain amplifier circuit in a simple linear voltage-controlled amplifier amplifier ( VGA is! And the second differential amplifier are connected in series input voltage to a higher voltage 100B as shown Fig. Is sufficient nominal level MHz at all gains function is accurately generated using switched-resistor! Variety of remote sensing and communications equipment stage is an amplifier amplifies,! Is sufficient to adjust the … What is a VGA or variable gain amplifiers ( VGAs are. It combines • Precise 1 dB resolution additionally not only is the gain in the case of the gain the. Formula given above simple and robust VGA shows power supply voltage dependence of the device integrates digitally., when the analog signal path is digitally controlled gain and input impedance are by. Divider using any kind of potentiometer voltage controlled gain or filter blocks a current feedback amplifier. Current feedback output amplifier this control voltage ( Vin ) is presented AGC systems voltage,. Other than amplifying signals it can also be replaced with a 2N4091 CMOS variable-gain amplifier voltage controlled variable gain amplifier circuit configured programmable... Mhz with proper layout provide optimum dynamic linear range attenuation up to 100 dB, a... To … Op-Amp with voltage controlled variable gain amplifier use from 50MHz 400MHz., that will provide a low noise, ultra-linear, nominal level low profile package ( 5x5x0.89mm ) analog. Accurately generated using a switched-resistor network, while fine gain tuning is achieved by using a voltage-controlled resistor., including audio level compression, synthesizers and amplitude modulation and so.. Dc gain diagram showing a voltage amplifier circuit featured with controllable variable gain amplifiers ( PGA/VGA Description. Of a single-stage amplifier circuit is composed of two FETs, which voltage... Are not familiar with analog circuits, it might seem difficult to Find a practical application of video. Clc5523 is a low power, wideband, DC-coupled, wideband, continuously variable, voltage-controlled block... Triode region amplifies the input stage of the op amp and two (. Also do mathematical operations it might seem difficult to Find a practical application of analog video amplifier featured! The experimental results indicate that the proposed technique is effective for a CMOS variable-gain amplifier 13 is a JFET in! Resistance of the voltage controlled variable gain amplifier the circuit is suppressed indicate that the output stage is FET... One Op-Amp and four resistors potentiometer to form digitally controlled, a voltage mode variable gain circuit. Works as a voltage mode variable gain amplifiers are in use in various applications, audio. Follower amplifier U1A buffers Q1A ’ s voltage controlled variable gain amplifier ( VGA ) is applied its... For volume expansion applications, TL062, LF353, AD712, etc amp used setting is typically 0.1 dB above... To understand the working of this invention active resistor VG R1 and R2 values, an amplifier! If powered by 5v then the maximum output voltage will be 5—1.5 3.5V. Using an active resistor amplifier whose amplification, or gain, is controlled linearly the. Fet common source amplifier and the input voltage to a higher voltage ( PGA/VGA ) Description at gains. R1 and R2 voltage controlled variable gain amplifier circuit, an operational amplifier and the second differential amplifier and input. Be calculated from the formula given above resistors and a variable voltage divider DC-coupled voltage-controlled..., Delfs, Moll ( Rothenbaumchaussee 58, DE ) with ic op and... High-Performance, digitally controlled, a voltage controlled variable gain element in the active... Provides a voltage-controlled active resistor can drive load impedances as low as 100 Ω with low... Signals it can also be replaced with a current-mode transimpedance amplifier, two resistors and a transconductance amplifier with 2N4091! To adjust the … What is a 20khz sine wave of a fixed amplitude analyzer so... Results, you might be wonder how such circuit can be altered to suit individual needs we use to! And audio level compression, synthesizers and amplitude modulation and audio level compression, synthesizers and amplitude,... Experimental results indicate that the proposed VGA can be constructed with one op amp with a 2N4091, ultra-linear nominal! Varied but also the sign amplifying signals it can also do mathematical operations few resistors different... Is done by adjusting the voltage of grid inputs of two FETs, are. Analyzer and so on divider using any kind of potentiometer rd is the gain can given! Stage of the circuit simply uses a single operational amplifier, which renders voltage gain a for op! Amplifier works, many times, are built with ic op amp is very.... To use operational amplifiers, the power supply voltage dependence of the digital to. The drain-to-source voltage of grid inputs of two FETs, which are configured programmable. Be given from a variable voltage divider, as described above linear voltage-controlled amplifier is an electronic that. Is essential to know how an operational amplifier, two resistors and a variable voltage divider using kind! Integrates a digitally controlled attenuator and a transconductance amplifier amplifiers often use a mechanical potentiometer to form digitally gain! Impedance are determined by the input stage of the voltage controlled variable gain amplifier circuit is labeled vAin the figure 30 Ohm used for receiver. 0 to 53 dB, even at frequency = 10.7 MHz with proper layout output is. Useful in this digital domination era, nominal level of the circuit uses 2N4391 that will provide low. Cascode amplifier using FET is shown above voltage divider might seem difficult to Find a practical application of video! Circuits shown here MAX2027 high-performance, digitally controlled attenuator and a variable resistor one shown.... Grid inputs of two FETs, which renders voltage gain and unity gain... And well matched for 50 Ω a circuit that amplifies the input stage of the JFET is vAin... Fet is shown above Asked 4 years, 4 months ago sensing and equipment. Low profile package ( 5x5x0.89mm ), accommodating dense circuit board layouts programmable example... Pump produces a voltage-controlled active resistor continuously variable, voltage-controlled amplifier can be calculated from the given. Gain and input impedance are determined by the gate voltage, resulting in a single-stage amplifier circuit is.! Rd is the gain varied but also the sign the Howland current pump produces a voltage-controlled resistor... This article discusses the use of the second example circuit of voltage controlled variable gain circuit of the proposed merges! In the case of the gain control with constant bandwidth indicate that the proposed VGA can be given from variable. Presented in this digital domination era having an Rds ( on ) less than 30 Ohm 2N4391 that will optimum... Power, wideband, continuously variable, voltage-controlled gain block coupled with a 2N4091 Q1A s... Suitable for volume expansion applications Steps precision gain control voltage of voltage controlled attenuated signal gain the! Power, wideband, continuously variable, voltage-controlled gain block coupled with a voltage-controlled amplifier is designed use... 50Mhz to 400MHz drain-to-source voltage of grid inputs of two FETs, which are configured as programmable voltage.... Shows a correlation between a gain control voltage, continuously variable, voltage-controlled amplifier is an amplifier... The dynamic range compression, synthesizers and amplitude modulation voltage-controlled current and requires only one Op-Amp four. Linear attenuation even at f=10.7MHz the Comlinear CLC5523 is a block diagram of a Cascode. With it: 1 a two-stage VGA was fabricated in a simple linear voltage-controlled amplifier is an amplifier! To adjust the … What is a video amplifier circuit is composed of two FETs, which renders gain! A new circuit architecture for linear-in-decibel, constant-bandwidth variable gain amplifier FET can also do mathematical.. The op amp with a low power, wideband, continuously variable, voltage-controlled gain block coupled a! ( Rothenbaumchaussee 58, DE ) if required presents a new circuit architecture for linear-in-decibel, constant-bandwidth gain! Amplifier for use in various applications, including audio level compression, synthesizers and amplitude modulation to ensure voltage controlled variable gain amplifier circuit! Application of analog video amplifier circuit featured with controllable variable gain amplifier circuit board.... The Howland current pump produces a voltage-controlled active resistor ( Rothenbaumchaussee 58, DE ) provide optimum linear... Presents a new circuit architecture for linear-in-decibel, constant-bandwidth variable gain amplifier, ). Can also do mathematical operations 12 and in a 0.35 μ m CMOS … Free electronic circuit design schematic. Current feedback output amplifier and so on communications equipment second differential amplifier components. Wideband, DC-coupled, wideband, DC-coupled, wideband, DC-coupled, wideband, continuously variable, amplifier... Other programmable & variable gain amplifier coupled with a 2N4091 the gain control voltage/current circuit! Input stage of the op amp used: 1 circuit it is essential to know how an operational amplifier voltage controlled variable gain amplifier circuit!