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signal source and an input channel on the MIC-3716. In this figure,
each side of the floating signal source is connected through a resistor
to the AIGND. This connection can reject the common-mode voltage
between the signal source and the MIC-3716 ground.
Fig. 3-4: Differential input channel connection - floating
signal source
This connection has the disadvantage of loading the source down with
the series combination (sum) of the two resistors. For r
and r
for
,
a
b
example, if the input impedance r
is 1 kΩ, and each of the two
s
resistors are 100 kΩ, then the resistors load down the signal source
with 200 kΩ (100 kΩ + 100 kΩ), resulting in a –0.5% gain error. The
following gives a simplified representation of the circuit and
calculating process.
39
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