Rob Robson wrote:

> Besides power supply noise, the only other difference betwee n the
> functioning legacy circuit and the faulty new one is the impedance
> they're each looking into: 2.7k for the former; 22k for the latter. Does
> anyone have any ideas about what might be causing the op amp to latch
> up? 

Not really. But possibly you're one step further if you check whether your
circuit works with a 3k resistor from the output(s) to ground (so simulate
the earlier impedance). 

What did you change to cause the impedance change?

Gerhard

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