October 2014

DocID026915 Rev 1

1/19

19

AN4586

Application note

Signal conditioning, differential to single-ended amplification

Sylvain Colliard Piraud

Introduction

There is a wide range of applications for which we need to amplify a differential signal and

convert it into a single-ended signal. Such applications can be used to condition the signal

of Wheatstone bridges, current measurements, or other small signal sources that require an

accurate measurement which rejects input common mode voltage (Vicm).

There are different ways to amplify a differential voltage into a single-ended signal. In this

document we will see the three more flexible methods that are based on operational

amplifiers (op amps):

• Differential amplifier

• 2-op amp instrumentation amplifier

• 3-op amp instrumentation amplifier

For each configuration, the output voltage is calculated to include the inaccuracies due to

the external components (the resistors) and the op amp itself. The common mode rejection

ratio (CMRR) is also calculated. If we consider a perfect op amp and if the resistors are

ideally matched, the CMRR should be infinite.

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