60 kΩ

60 kΩ

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V

S–

Internal

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-

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S-

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V

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60kΩ

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THS4532

www.ti.com

SLOS829 – FEBRUARY 2013

Input Common-Mode Voltage Range

The input common-model voltage of a fully differential op amp is the voltage at the “+ and –“ input pins of the op

amp.

in linear operation the voltage across the input pins is only a few millivolts at most. So finding the voltage at one

input pin will determine the input common-mode voltage of the op amp.

Treating the negative input as a summing node, the voltage is given by:

(1)

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.

Setting the Output Common-Mode Voltage

the output common-mode voltage as close as possible to this voltage. If left unconnected, the output common-

mode is set to mid-supply by internal circuitry, which may be over-driven from an external source. Figure 78 is

for best performance, but it is intended to be a DC bias input pin. Bypass capacitors are recommended on this

pin to reduce noise. The external current required to overdrive the internal resistor divider is given approximately

by the formula:

(2)

Copyright © 2013, Texas Instruments Incorporated

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