Virtual op amps CC does not function.

Question

Problem Description :
The virtual op amps do not function properly. I entered the parameters for the Max9910 op amp to check the GBW product. I had to increase the Fu to 2x the stated value.
The Compensation Capacitance value has not effect on the simulation.
Also, please define the (VSW+) and (VSW-) parameters in the virtual model?
Steps To Reproduce :
See attached file
Workaround :
Trying to use an op amp model Max494 and change the model parameters to match the Max 9910 opamp, but I do not know which parameters to change for Fu?
What
are G1, G2, and G3? R1, R2, and R3? Max494 spice model model is below.
* EWB Version 4 - 3 Terminal Opamp Model
* A= 251188 RI= 3e+006 RO= 1000 VSW+= 6.85 VSW-= -20
* Vos= 0.0002 Ibs= 2.5e-008 Ios= 5e-010 SR+= 200000
* fu= 500000 fp2= 1e+032 CC= 3.9e-011
Vos 4 1 DC 0.0002V
Ib1 4 0 2.525e-008A
Ib2 2 0 2.475e-008A
G1 0 5 4 2 0.0630957
G2 0 6 5 0 0.0630957
G3 0 3 6 0 0.0630957
Ri 4 2 3e+006ohm
R1 5 0 1000ohm
R2 6 0 1000ohm
R3 3 0 1000ohm
C1 5 0 7.99556e-005
C2 6 0 1.59155e-036
Cc 5 0 3.9e-011

Answer 1

What i see is a differentiated waveform on the output of the first circuit when I get it working. This tells me that there is a capacitor in the circuit creating this waveform and most likely it is across the feedback resistor. You have to take into consideration that these are perfect models with no parasitic capacitance modelled with in them and you have no other capacitance in your circuit  Also you are applying a square wave to this op amp and the compensation capacitor, with no other capacitance in the circuit, is causing the output waveform to differentiate.
It seem to be there and is working, but not maybe the way you would want it to.
Anyway, I would like to hear form NI and see what they think about both of these situations when it comes to the virtual op-amps
Message Edited by lacy on 12-15-2007 11:28 AM
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