[sdiy] op amp phase inversion

[Czech Martin]

{
Some op amps show an anoying behavior: their common mode input range is
limited (lower then  + - supply). If the limit is reached, the input
transistors get into heavy saturation and the noninverting input gets
inverting, the other will be noninverting. Thus the name phase reversal.
In noninverting apllications this can lead to (soft) latch up:
the output goes to one rail and will stay there until power is removed.
Or in other words: if the input amplitude of such an application
goes too high, the amplifier will latch.
The explanation applied to bipolar input stages. But JFET op amps
can show this behaviour as well. I guess it happens when the gate implantation
is forward biased.
But not only linear applications are affected: a latching op amp
is also useless in comparator applications.

Finally the latch up can lead to a too high differential input voltage,
destroying the input junctions. In this case (soft) latch up 
is not really that soft...

This kind of latch up should not be confused with CMOS latch up,
where a parasitic SCR is triggered wich will short the supply
and fry the PSU or chip or both...
}

>From the datasheet one can not really tell if the op amp will latch or 
not. E.g. I could not see a problem in the TL071 data sheet,
nevertheless, the device will latch and it will also fail as comparator.

So, is there a information resource which op amps do latch and wich
don't on the web or elsewhere?

LF356
TL06X, TL07X, TL08X, TL05X
741
RC4136
...

m.c.