What is the difference between VGA and AGC?

In the transceiver circuits,

what's the difference btw VGA (Variable Gain Amplifier) and

AGC (Automatic Gain Controller) ?

I'm confused.....

Thanks.

VGA + level detector + feedback loop = AGC

AGC will give a fixed amplitue output, but VGA only give gain.

So uasualy, VGA is a part of AGC.

For example VGA gain is form 10dB to 70dB.


if you want a -20dB output, but he input is -70dB.

So the gain will be 50dB auto contralled by AGC.

agree with FVM , the VGA is a part of AGC loop
the AGC loop is a feedback loop , which make the output ampliftude is always constant as the input chanege so it employ a VGA

khouly