Help for variable gain control???

[Mike Belanger]

I'm building an automatic gain control (AGC) circuit using Simulink,
but can't seem to find a block to allow me to properly simulate my
model. The idea is to have an AC input signal (sine wave) into a
variable gain block, create a DC signal from the amplified AC signal
(which I have done), and then feedback this DC signal to the variable
gain block to control the amplitude of the output AC signal from this
variable gain block. The output should be constant despite a
changing amplitude in the input sine wave.

Is there a component in Simulink that will allow for this variable
control of the gain of an AC input signal (ie. produce an AC signal
with a fixed gain using a feedback DC signal)? I'm not having any
luck building this part of the circuit.

Any help or ideas with this would be greatly appreciated.

[Vivek Nadkarni]

Hi -

I am not sure I understand your question. However, I think that you
want to know if you can create a variable gain block in Simulink.

You can use the multiply block in Simulink to behave like a variable
gain block. It has two inputs and outputs the product of the two
inputs.

Did that answer your question?

Vivek

[Mike Belanger]

Thanks, Vivek. You're right in understanding that it is a variable
gain block that I am trying to implement.

The multiplier is an interesting approach that might just give me
what I'm looking for. However, I want the output from this block to
always be the same value, despite the changing amplitude of the input
sine wave. I will definitely give this a try to see if it's the
right fit.

Thanks again,

Mike