[sdiy] "latch up" and TL071, LM324

[Czech Martin]

I have tortured the TL071 and LM324.

The TL071 shows phase inversion if the input comes close
to the lower rail. This will prevent proper comparator action
in some applications.
A unity gain buffer with 10k feedback resistor and 10k protection
resistor to +  did not really latch, but the device started oscillating
when the input was close to the lower rail.
Perhaps, with other parasitics it may as well really latch.
In my test circuit I was able to move it away from the dangerous
zone.

So the TL071 input is not able to operate near the negative rail,
noninverting circuits will tedn to oscillation, if not latch up.

Not such a good idea for an "audio" chip...

The LM324 (like most bipolars) behaves well.
It does not show any phase inversion. As comparator it will
work very close to the rails.


m.c.