necessary to min i mize gain error. Also, any mis match be tween the
total source re sis tance at each input will af fect gain ac cu ra cy and
common -mode rejection (CMR). For ex am ple: when operating at
a gain of 10, an 80
mismatch in the source re sis tance between
the inputs will degrade CMR to 68 dB.
The output buffer, A2, operates at a gain of 2 or 20, thus setting
the overall, precalibrated gain of the AD626 (with no ex ter nal
com po nents) at 10 or 100. The gain is set by the feedback net work
around amplifi er A2.
The output of amplifi er A2 relies on a 10 k
resistor to –VS for
“pull-down.” For single-supply operation, (–VS = “GND”), A2
can drive a 10 k
ground ref er enced load to at least +4.7 V. The
min i mum, nominally “zero,” output voltage will be 30 mV. For
dual-supply op er a tion (±5 V), the positive output voltage swing
will be the same as for a single supply. The negative swing will be
to –2.5 V, at G = 100, limited by the ratio