Re: Conceptual design of a constant volume control opamp circuit

On Jan 30, 3:24 pm, "MRW" <mr.whate...@xxxxxxxxx> wrote:
Good day:

I don't know how to word these properly. I'm really confused right
now. I'll try. If I were to design a single supply constant volume
control opamp circuit, would it be right to assume the following:

- In coming up with a conceptual block diagram, I take a sample of the
input signal and compare it to some threshold value. If the signal is
not equal to the threshold value then change the gain so that it
becomes equal to the threshold value. However, I'm not sure if this is
a valid assumption, since I would need to have a very fast opamp for
the gain to change instantaneously before the next instantaneous
input. I guess for audio inputs most opamp would be fast enough to
change the gain.

- The VCA that I have has its gained controlled by two voltages via
the following relationships: Vcn+ - Vcn-. I was thinking of setting
Vcn- at a fixed voltage, and use Vcn+ for the controlling voltage.

- For threshold circuit, I was thinking of using a differentiator. The
output of this differentiator would be sent to another opamp circuit
with an output voltage reference to a value equal to Vcn-. The output
of this opamp would be connected to Vcn+.

I can't help with your specific application.
In the old radio days it was called Automatic Gain Control (AGC)
Also consider searching the phrase "foldback limiting" used in DC
power supplies.

.

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