[sdiy] op amp phase inversion

[René Schmitz]

Hi Martin,

>>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.

Only you use it outside the range of allowed input common mode voltages. 
And those *are* spec'ed.

Be conservative and don't allow your circuit to go into that region.

Choose constructive measures against it. E.g. use an inverting 
configuration instead of a noninverting one, because it doesn't have 
that problem. (If the noninverting input is within the common mode range 
that is.)

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

As usual the manufacturers don't say what happens when exceeding the 
ratings. It could latch, or turn into an elephant. :-)

I'd say if you need proper operation near the rails, then pick a type 
whose common mode range includes that rail. There are quite some where 
that range includes one of the rails. (But usually not both.)
There is a nice table in the "Art of Electronics" which includes that 
information.

Cheers,
  René


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uzs159 at uni-bonn.de
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