AGC Design

[Mark Atom]

I designed a simple AGC circuit that took the output from a detector and
fed it into an inverting op-amp integrator (- input). On the + input, I
connected an adjustable reference voltage. The reference allows me to
adjust the output level of the AGC. The inverting integrator is followed
by an inverter stage and connected to the AGC amplifier. I adjusted the
integrator gain and got it working well. My breadboard used op-amps
with split supplies.

Now I find out that there was only a single supply made available to
power the AGC circuit, so I'll have change op-amps and use a single
supply design.

I found and evaluated some non-inverting integrator circuits and I think
they will work OK for my design since the bandwidth is low.

My question is how do I connect the detector output AND the reference to
the non-inverting integrator so a comparison can be made?

Mark

 

[PeteS]

I designed a simple AGC circuit that took the output from a detector and
fed it into an inverting op-amp integrator (- input). On the + input, I
connected an adjustable reference voltage. The reference allows me to
adjust the output level of the AGC. The inverting integrator is followed
by an inverter stage and connected to the AGC amplifier. I adjusted the
integrator gain and got it working well. My breadboard used op-amps
with split supplies.

Now I find out that there was only a single supply made available to
power the AGC circuit, so I'll have change op-amps and use a single
supply design.

I found and evaluated some non-inverting integrator circuits and I think
they will work OK for my design since the bandwidth is low.

My question is how do I connect the detector output AND the reference to
the non-inverting integrator so a comparison can be made?

Mark

You have a couple of choices

1. Feed the detector output AC coupled to the amp and DC bias the amp at
V/2.

2. Get a cheap ( < $1 ) switched cap inverter to produce your negative
supply. TI makes some good to 60mA in a SOT-23. National, Maxim and
Linear tech (to name just three) also make such things.

Cheers

PeteS