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chopper amplifier, feedback feasible?

Hello all,

I want to implement a chopper amplifier (differential input, single output) into a follower topology. Since a chopper amplifier works by square wave modulating the input (chopping, originally by a mechanical switch), amplifying the resultant AC signal, and then synchronously detecting the amplified signal.... (copied this bit from another post), is a follower topology (minus input shorted with output) feasible with a chopper amplifier, or will the feedback destroy basic chopper amplifier principle?

In other words, can a chopper amplifier be operated only in "open- loop" mode (no feedback), or can the chopper amplifier replace op-amps in typical op-amp topologies, meaning that it can handle feedback.

I am using the chopper amplifier to remove a signal's flicker noise. This is why I am employing the chopper amplifier in a follower topology.

Any help will be appreciated.

Regards,

-Roger

Reply to
Roger Bourne
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I'm not sure if you have got the concept straight. Besides, I can't see how any kind of amplifier can help you "remove" any kind of noise from a signal. If all you want is an amp with very low 1/f noise, maybe a chopper stabilized opamp is what you need.

robert

Reply to
Robert Latest

I just read some more on chopper amps (....prompted by your comment :-)). I get it now, chopper amps remove/attenuate the 1/f noise contribution of the amp only. Hmmm..... I guess I will have to find a way to introduce the the chopper amp in the feedback loop that is responsible for producing the very-noisy 1/f signal. That should not be too difficult (i hope) since the noisy signal stems from an op- amp in follower configuration. That brings me back to my original question, can chopper amps function with feedback ?

-Roger

Reply to
Roger Bourne

On 5 Apr 2007 08:04:31 -0700, Roger Bourne wrote

Without knowing any more about the kind of signal being processed, this brings me back to my original suggestion: Read up on chopper-stabilized opamps (very different from chopper amps which have gone out of fashion decades ago). Possibly you can just replace your noisy opamp follower by dropping in a chopper stabilized one and be done.

When doing research on this, you can also look for "zero drift" opamps which is another name for the same thing. LT have a few cute app notes on their site

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robert

Reply to
Robert Latest

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