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Circuit fail to converge

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chw82

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I have try out a few option provide from the forum eg. STEPGMIN, increase ITL1=400, changing OP-AMP open loop to 1e-5. Attached is the schematic and hope someone will help.

Appreciate any help given.View attachment Power_Supply.zip
 

keith1200rs

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Are you sure you have power connected to the opamps? - I cannot see any connections, nor any node names that might match the default power supply pin names.

Keith.

---------- Post added at 09:57 ---------- Previous post was at 09:45 ----------

You don't seem to be using opamps. Looking at the netlist you are using

Code:
E_U1         N04831 0 VALUE {LIMIT(V(N03028,N04557)*1E5,-15V,+15V)} _U1 N03028
+  N04557 1G
as an opamp. I think that is the source of your problem.

You would probably do better with an opamp model, even an "ideal" one.

Keith.
 

chw82

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those opamp do not have supply pin out. We need to double click inside the properties and set out supply there. The text file do display the supply value (+/- 15V).
 

keith1200rs

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As I said above - try a "real" opamp model. What you are using is something with infinite bandwidth and a gain of 180dB which is a bit extreme.

Keith.
 

chw82

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i have used a real opamp (TL071) and it work.
BTW, im curious why it not able to work even i have change the open loop gain to 80dB?
 

keith1200rs

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It may not be just the gain that is causing the problem. You also have infinite bandwidth and an abrupt limit when the output reaches the supply voltage.

Keith
 

chw82

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thanks a lot.
May be i need to take a look on the opamp spice model text file and play around with the number.
 

keith1200rs

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If I want an 'ideal' opamp for some quick simulations I usually use an E source with a gain of 60 or 80dB and add a single pole filter to the output - simple RC with a low R. No voltage limits.

Keith
 

LvW

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It may not be just the gain that is causing the problem. You also have infinite bandwidth and an abrupt limit when the output reaches the supply voltage.

Keith
Yes, I agree with Keith. Sometimes I've made the same experience using the "OPAMP" model in PSpice that provides hard output limiting. Mostly for transient simulations with output amplitudes that reach these limits I have observed such convergence problems.
 

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