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Amplifying strong signal and Op-Amp saturation

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iewgnem

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Hello, my first post and a simple question I can't seem to find the answer elsewhere.
So I need to amplify an RF signal, but its power range from +15dBm to -120dBm

The system need to input a 2.5DC 1V p-p signal into the ADC for frequency analysis, but I'm not so sure how to amplify the signal for such a large dynamic range. If I use an Op-Amp chain with a limiting stage at the end, what if the signal is strong and a stage before the limiting amp reaches saturation? I don't think most such systems use all limiting amplifiers, but then how did they do it?

Any ideas?

Thanks.
 

flatulent

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You will need an amplifier chain with variable gain. You cannot get an ADC with ten million counts.
 

iewgnem

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I know I could use AGC, but since I only care about information on the frequency domain, I do not need to adjust the signal power precisely, only so that I can restore the original frequency information at the end. I believe most FM receivers do not have AGCs built in and they are relatively expensive. I'm just wondering if its considered an acceptable practice to drive RR opamps to their rails or is there a much simpler way of solving this problem
 

A.Anand Srinivasan

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you just gotta take care that the latchup doesn't occur.... so i think it is enough if you just take care that the input of the opamp doesn't go beyond the supply rails...
 

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