Does the op amp model in PSPICE include the effect of saturation recovery?

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powersys

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An op amp’s recovery time measures how quickly it returns to a linear mode from a state of saturation. Does the op amp model in PSPICE include the effect of saturation recovery? Many thanks.

 

What's "the op amp model in PSPICE"? You have to ask for specific models.

Generally speaking, OP models don't represent all behavioral aspects. Most of the recovery time will be generated by overload of the internal frequency compensation circuit, which must not necessarily correctly modelled in a functional model. A transistor level model can be expected to model it realistically.

The easiest way is to check the recovery behavior of the interesting OP model yourself.

P.S.: The attachment of your post just reappeared. Apparently you are using a simplified infinite bandwidth OP model which hardly shows realistic recovery.
 

I assume that the op amp shown in the figure is an ideal model.

It's used to construct an op amp differentiator. When a squarewave input is applied, theory predicts that the output should consist of "spikes" which are corresponding the the rising/falling edges of the input squarewave. The output of the differentiator (built using the PSPICE ideal op amp model) does NOT follow exactly what the theory has predicted. It looks to me that the weird output is due to saturation recovery effect. But I thought an ideal op amp should not have saturation recovery issue, isn't it? I will post some simulation results later. Many thanks.
 

You are slowly approaching a clear question.

Besides possible overload recovery of the OP, which doesn't exists for the ideal model, there are overload effects of the circuit itself. Watch the voltage at the inverting OP input to understand what's happening.
 

Some simulation results:

CASE-A:
Power supplies of the op-amp, ±Vs = ±15V.

CASE-B:
Power supplies of the op-amp, ±Vs = ±100V

Observation:
When ±Vs is higher, the width of the "spikes" (which are corresponding to the rising/falling edges of input squarewave) becomes smaller, or closer to "ideal spikes" as predicted by theory.
It looks to me that this has something to do with the "saturation recovery" of the op-amp. Hence, is the PSPICE op-amp I used an ideal model or does it include saturation recovery effect? Kindly advise.

Many thanks.






 

It looks to me that this has something to do with the "saturation recovery" of the op-amp.
Click to expand...
No. It's a simple non-linear effect of the circuit.
Watch the voltage at the inverting OP input to understand what's happening.
Click to expand...
 
FvM said:
No. It's a simple non-linear effect of the circuit... Watch the voltage at the inverting OP input to understand what's happening...
Click to expand...
I see your point now. Really appreciate for your help.
 

A late comment. If you are seeing large differential input voltages between the op amp inputs when the output clips, sometimes putting two parallel, high speed, Schottky diodes between the inputs can clip this signal and speed up recovery. I use a dual BAT54 if I remember correctly. In normal (linear) operation, the diodes effectively disappear because the differential input is small.
 

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