I'm looking for a cheap quad opamp with the same pinout as the LM324.
The killer is that I want one with a high input bias current. I'm
using a LM324 (LM224 actually to get the high temperature capability)
at the moment as a sensor amplifier and use the voltage rise caused by
the bias current to detect if the sensor goes open circuit.
Trouble is that some of the existing opamps have sufficiently low bias
current to balance the leakage current and don't hit the sensor fail
threshold. If I use a high speed opamp like the MC33274 it works fine,
every time but a) costs more and
b) is so much higher in transition frequency that I'm worried the RF
immunity will suffer. -  I'd probably have to get the item retested.
I can add additional pullup resistors but that would mean a pcb change
and also (probably) retesting. So I'm looking for a cheap quad opamp
with a transition frequency in the 1 MHz  area with a minimum input
bias current somewhere around 100nA or higher

Richard P
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