AN4586 Datasheet, PDF (1/19 Pages) STMicroelectronics – Signal conditioning, differential to single-ended amplification

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.
October 2014
DocID026915 Rev 1
1/19
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