Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

Questions tagged [voltage-controlled-amplifier]

For questions about voltage controlled amplifiers (VCAs).

For questions about voltage controlled amplifiers (VCAs).

22 questions
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Digitally-Controlled Analog Processing for VGA Video Signal?

A few months ago, I replaced the dead fluorescent backlight of an LCD computer monitor with an 8-bit-per-channel RGB LED strip, and built a controller for it from an AVR microcontroller that talks to the same Raspberry Pi that drives the screen. …
AaronD
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3 answers

Design of an Automatic Gain Control Using a JFET

simulate this circuit – Schematic created using CircuitLab I have implemented the above circuit which is supposed to amplify a negative 200kHz sinusoid to constant amplitude even if the amplitude is varied. The constant amplitude is adjusted…
Simon Sultana
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Long tail amplifier using current mirrors

I have built this in the Multisim simulator and it works there as desired. Now I have built it on a "lame" breadboard. Is the upper PNP current mirror correct? Since the "left" leg behaves opposed to the "right" leg when in working order, the…
NaturalDemon
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1 answer

What's the purpose of this circuit section?

I'm experimenting on VCA circuits and found the same (or similar) pattern in many linear VCA projects found in internet using LM13700 OTA. The specific section I'm curious is made by an Op-amp, a transistor, a diode and some passive parts, and is…
Adam Calvet Bohl
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Why does this JFET attenuator distort the signal this way?

I have been trying to build a simple VGA using an op-amp and JFET for gain control. I get good results over a small range of voltages (like factor of 10) but as soon as I try to improve this, the signal gets distorted in on or another way. I figured…
Felix S
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LM13700 does not completely reduce the sound

I have a problem with LM13700 - it does not completely reduce the sound when the control current is zero. For testing, I put together the most basic circuit, where the control pin is connected to the ground. In my understanding, this should block…
Alex_G
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Single transistor VCA for gate type CV signals

I am in the process of designing a sort of mini synth / noise machine and I'm struggling with the output stage. I only want sound to come out when I press the button, so based on some designs I have found on the internet I have come up with this.…
Javier Soto
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Drive a VU meter negative from "0dB" to show compression with VCA compressor

I have a simple VCA compressor based around the THAT 2180 VCA. http://www.thatcorp.com/datashts/dn115.pdf I would like to use a standard "VU meter" to indicate compression, but work in "reverse." Meaning, the VU meter rests at "0" then moves to the…
jackwarner
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LM13700 control current appearing as voltage at output?

I've got an LM13700 in this VCA configuration, and for whatever reason the gain control input (I'm applying a triangle LFO, ranging from 2-7v) is appearing as a voltage at the output. Does anybody know why this could be happening? :
Jonathan Donald
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Having trouble with OTA CA3080 making a VCA

I'm having trouble getting this CA3080 OTA to work properly. :-( I watched this video ( https://www.youtube.com/watch?v=BbaJ6TOmyVo ) which is quite helpful, but I'm missing a few cues here... In the enclosed picture you find the circuit as I think…
user3810130
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Trying to make fuzz factory with CV inputs

I'm trying to construct some kind of fuzz factory modular from regular fuzz factory pedal. Circuit of the original pedal is pretty easy, but I've tried to add some VCAs based on LM13700. Honestly, I'm a little noob in electrical design, so I've…
drdrvv
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How to understand V2164 VCA control voltage per dB?

I'm designing an audio circuit which includes the V2164 VCA IC. This chip is a clone of SSM2164. I take a "Basic VCA Configuration" circuit which is supposed to give a unity gain with 0V control voltage level. The datasheet says the chip has "a…
Volodymyr Smotesko
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Fine-Tuning a Circuit After changing VCA (SSM2641 to SSI2164)

A friend's accident led to a fried SSM2641 VCA in an Eurorack audio module. Determined to give it a new lease on life, I'm diving in, though VCAs are not my forte. After searching for hours, it seems there's no direct "plug and play" replacement…
flower.fish
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LTspice simulation with diode in op-amp feedback does not match reality. why?

I want to change the curve characteristics of a vca-input signal (DC). So I simulated a circuit that I found on the internet (which is part of a commercial device so I suppose it should work): The results of the simulation in LTspice are fine and…
linsensuppe0815
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Voltage-controlled amplifier output offset

I'm testing a voltage controlled amplifier circuit in a simulator. The circuit is powered by a single 9V supply, so a "virtual ground" equal to 1/2 VCC is used. I have a question about the output of this circuit. Due to the virtual ground, the…
Alex_G
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