Questions tagged [cmrr]

Common-mode rejection ratio (CMRR) is the measure of rejection by the device of unwanted input signals common to both input leads, relative to the wanted difference signal.

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Why is CMRR effect multiplied by gain in this non inverting op amp configuration?

In this document Vout of a non inverting op amp is given as follows: But why \$\frac{V_{in}}{CMRR} \$ is also multiplied by the gain? I would write it as: \$ V_{out} = \big[1 + \frac{R2}{R1} \big] \...
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4answers
754 views

operational amplifier CMRR measurement

I am trying to measure CMRR of an op-amp and I found an application note from Analog Devices, that suggests the circuit below. I understand what CMRR means, but I can't understand why in the formula ...
6
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2answers
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Why is noise is considered to be a “Common Mode Signal”?

I learnt that the magnetic interference due to the Earth causes noise in the cable but I wonder why this is considered to be a 'Common Mode Signal' and why differential amplifiers are used to ...
2
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2answers
2k views

Op Amp CMRR problem

I'm studying on my own for an exam. I bumped into this problem that really got me. My answer just doesn't match. Find the CMRR of the operational amplifier above, consider Ad = 1000000 (Answer CMRR= ...
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1answer
205 views

Effect of bias resistor value on common-mode rejection in a differential or instrumentation amplifier

In the below schematics a source is coupled to a differential amplifier. Rb is a bias resistor for bias currents to flow: Since in instrumentation amplifiers it is a remedy to add resistors for bias ...