SK2-V 008059 with new matched (<10mV) 6SD4 nuvistors. 3-20-6
supply vout vinm vinp=0V after warmup stabilization. Gain=20x, Rf=2meg,Ri=100k
300 909mV 43.3mV
250 303mV 14.6mV
200 142mV 8.3mV
150 619mV 29mV
100 1680mV 79.6mV
50 1101mV 29.9mV
25 710mV 20.0mV
The following plot shows that the input and output offset voltages don't track very well at low supply voltages. Perhaps something to do with the behavior of input leakage currents on the 2Meg feedback resistor.