SLOS823D December 2012 – March 2020 THS4531A
PRODUCTION DATA.
The input common-model voltage of a fully differential op amp is the voltage at the positive and negative (+ and –) input pins of the op amp.
Do not violate the input common-mode voltage range (VICR) of the op amp. Assuming the op amp is in linear operation, the voltage across the input pins is only a few millivolts at most. Therefore finding the voltage at one input pin determines the input common-mode voltage of the op amp.
Use Equation 1 to calculate the voltage with the negative input as a summing node.
To determine the VICR of the op amp, the voltage at the negative input is evaluated at the extremes of VOUT+.
As the gain of the op amp increases, the input common-mode voltage becomes closer and closer to the input common-mode voltage of the source.