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question of design - RF Cafe Forums
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knightoftheparadise
Post subject: question of design Posted: Tue
May 02, 2006 2:45 pm
Lieutenant
Joined: Tue May 02, 2006
2:26 pm
Posts: 1
how can we design a automatic gain control circuit
for amplifier?
Top
fred47
Post subject: AGC amplifierPosted:
Tue May 02, 2006 6:26 pm
General
Joined: Wed Feb
22, 2006 3:51 pm
Posts: 104
Hi!
You need two things for an
AGC amplifier:
1. A way to measure the signal strength, and
2.
A way to vary the gain based on that measurement.
AGC amplifiers
come in two varieties, feedback (closed-loop, more common) and feedforward
(open-loop, less common).
Signal strength measurement is often
done by rectification followed by low-pass filtering.
There are
two major ways to vary amplifier gains:
1. Varying the operating
parameters of a BJT or FET
2. Using a FET or a PIN diode as a controllable
impedance
Within those two major ways are a large number of specific
approaches, depending on frequency, dynamic range, etc.
I hope
this helps.
Good Luck,
Fred
Posted 11/12/2012
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