Opamps latch up?

[cupoftea]

Hi,
We need an opamp for supply rails of +20V and -3v3.

One's a buffer, the other is used with negative feedback to give a certain voltage at the output of a linear regulator.

Can you confirm that none of the following opamps will ever latch up when they are given input voltages to either pin (inv or non-inv) , which is within the supply rails, but outside the common mode input range?

LM2902,
TL084C
TL084H
TL084X
TL074X
LM348
LM342

 

[FvM]

You are asking about latch-up or phase reversal? Latch-up never happens with input voltage inside supply rails.

 

[danadakk]

You referring to phase reversal ?

If not discussed in datasheet, typically in the applications section, then contacting
the vendor application group can answer this. of the field application engineer(FAE).

https://www.analog.com/media/en/training-seminars/tutorials/MT-036.pdf

https://www.ti.com/lit/ml/slyw037/slyw037.pdf?ts=1705275923730&ref_url=https%253A%252F%252Fduckduckgo.com%252F

Regards, Dana.

 

[D.A.(Tony)Stewart]

The FET input types are specified differently.
e.g. TL08x
Vs= +/-18V max

"(2) All voltage values, except differential voltages, are with respect to the midpoint between VCC+ and VCC−."

So for +20,-3.3V your midpoint is 11.65 V

"(4) The magnitude of the input voltage must never exceed the magnitude of the supply voltage or 15 V, whichever is less"

So (11+/-15) =+26V/-4 is greater than your supply. so OK.
Then for ESD protection.
"Input pins are diode-clamped to the power-supply rails. Input signals that may swing more than 0.5 V beyond the supply rails must be
current limited to 10 mA or less."

Only CMOS, SCR's and Triacs latchup

 

[cupoftea]

Thanks, the kindly supplied above says phase reversal stops once the input voltage comes back within the input common mode range...is this always the case, with all opamps?
Phase reversal, i always took it, means it goes to either rail.....but usually its the opposite rail to the breach of common mode range?

 

[D.A.(Tony)Stewart]

Did you read it ? Inversion does not mean saturation and not all OA's

 

[FvM]

Regarding original question about "latch-up". It has been emphasized that phase reversal due to exceeded common mode range as such doesn't involve latching behaviour. When the input voltage returns to common mode range, normal operation will be restored.

There's however a special case, if the amplifier is part of a feedback loop, phase reversal can lock the loop in saturated state.

 

[dick_freebird]

"Standard Linear" process op amps lack the kinds of structure that
enable SCR latchup. I would not assume any such thing about a
CMOS op amp, which likely would have the potential if not the
outcome of supply latchup (this depends also on layout and the
circuit).

Phase reversal, yeah, bad.

Regardless what a datasheet may or may not say (w/ fine print
footnotes) I would be on the bench abusing candidates along the
lines of the anticipated extremes of "stimulus".