I have a standard inverting amplifier stage with Rf = 100k and Rg = 10k (A = -10 V/V). The amp is powered from +/-5V and the positive input terminal is connected to 0V. Pins 1 and 5 are open. Pin 8 (nDISABLE) is also left open. Very straightforward setup.
The problem is that the output has a DC offset of -2.2V, but otherwise behaves as expected for AC signals. Tying the disable pin high has no effect. This was repeated on three ADA4897-1 parts and all were identical. Inserting a bias compensation resistor of 9kOhm between positive input terminal and ground brings the DC offset to about 100mV.
Without the bias compensation resistor, I swapped out the part for an AD8610 and the offset disappears and the circuit behaves normally. Interestingly, the offset voltage is absent when I use the ADA4897-1 in a basic non-inverting configuration (Rf = 247, Rg = 13, A = 20 V/V). Did I just receive a batch of bad parts, or is there something I'm missing specific to these components?
Thanks,
Jason