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