Measure/calculate CMRR of Audio Opamp

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Measure/calculate CMRR of Audio Opamp

Post by grievousangel »

I have a Picoscope 4262 and need to adjust the CMRR of an audio amp. The amp is a discrete DOA similar to SL-2520 as used in API-like studio gear.

Would differential probes help with these procedure? CMRR application notes?

Advice please.


Picoscope 4262

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Re: Measure/calculate CMRR of Audio Opamp

Post by Gerry »

Hi grievousangel,

I apologise for the delay in answering (this post got overlooked in the run up to Christmas).

For the precision that I assume you will be working with, you would probably need a low voltage active differential probe (to help probe relatively small, non-earth referenced voltages). The lowest voltage, probe less than £500 in our product line-up would be this x10 probe: ... tial-probe. So the answer to your question depends upon the precision with which you need to adjust the CMRR.

In all likelihood, a better solution would probably be to use a suitable differential Instrumentation amplifier module to condition the signal for the PicoScope 4262. Finding suitable Instrumentation diff-amp modules from reputable manufacturers that would be suitable for test and Measurement is a challenging task, but it is made easier by the likes of Analog Devices and Texas Instruments offering cost effective Instrumentation amplifier modules, such as this one: ... VM/2762244, some of which you can even purchase already populated (note that this is just a suggestion, as we have not verified any such devices for any specific use with our products).


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