# Blog

## What is a differential amplifier? ## What is the output voltage of a differential op-amp?

• Since all the resistors of differential op-amp is 10k it acts as a unity gain differential amplifier meaning the output voltage will be the difference of voltage between pin 3 and pin 2 of U2:A. The output voltage of the Instrumentation amplifier circuit can be calculated using the below formulae.

## How to offset the output of an InAmp instrumentation amplifier?

• The output can be offset by feeding an arbitrary reference voltage at REF, much like a standard three-op-amp instrumentation amplifier. The point to note is that the intermediate signal in the conventional three-op-amp InAmp contains both the amplified differential voltage and also the input common-mode voltage.

## What is common-mode rejection on a differential AMP?

• In reality, the two inputs on a differential amp have unequal gains. Accordingly, even with inputs that are equal, common-mode rejection is not absolute, and the amp would have an output that is non-zero. Taking this into account the equation for output voltage becomes: where A c is what’s called the amplifier’s common-mode gain.  