Help with AGC circuit

I'm designing an AGC circuit using Teledyne Cougar parts. The AGC amp is the AGC230, the detector is the DAC4101. I'm trying to hold the output of the AGC amp at -5 dBm. -5 dBm into the detector produces about .7 volts output. I used and error amp with a reference input connected to a gain stage to drive the AGC amp. This works OK, but not great. There is still some variation in the output of the AGC amp when the RF input changes. The detector output is linear over a wide range (-40 to +10 dBm), but the control voltage vs gain curve for the AGC amp is not. I suspect that I'm operating on a sensitive point of the AGC amps curve, where small changes in control voltage make large changes in gain. However, I thought that the Feedback path would then to linearize those changes.

Any help is appreciated.


Reply to
Mark Atom
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You might try increasing the gain of the gain stage to reduce the error. You might end up oscillating, but there may be some room before that happens.

-- John

Reply to
John O'Flaherty

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