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PSpice Convergence Problem

I have a circuit comprising one OP-77/AD op-amp that is basically a Sallen-Key filter with some other resistors and capacitors around it. All capacitors use a tolerance (10%) and all resistors use both a tolerance (1%) and a tempco (100 ppm/C).

I've had convergence problems during worst-case simulations at some temperatures. The OP-77/AD seems to be at the heart of the problem but I'm stuck with it because I'm analyzing an existing circuit.

All of the power supplies (+/-15V for the op-amp, and +5 for another item) have both 5% voltage tolerances and 200 mVpp noise at 20 kHz bandwidth.

I've made these modifications to the default simulation settings: VNTOL = 1E-4 ABSTOL = 1E-10 GMIN = 1E-9 ITL1 = 5000 ITL2 = 2000 ITL4 = 2000

Is there something else I should do to enhance convergence?

What about the solver? Is the default best? What are solver 0 and solver 1?

Is selecting GMIN stepping helpful?

Thanks,

Bob Penoyer

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Bob Penoyer
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SOLVER=0 is the old original solver before it was "new and improved". I have found the setting SOLVER=0 will often work on difficult circuits.

Sometimes ;-)

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
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Jim Thompson

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