NUPSSHAH,
I took a quick look at these circuits.
In 'sine wave generation.ms12' for U1A, you have pin 4 (V+) wired to Gnd and pin 11 wired to +6V (whereas all the other opamps are opposite). Is this intentional or is your circuit not correct?
Also, these appear to be of the self-resonant variety (where the 180 phase change is important) and may be difficult for any SPICE simulator to simulate, especially if the start-up conditions and phase (transfer function) is not perfectly modeled. I think this may be similar to a situation where in SPICE you need to 'kick-start' a resonant crystal, ie - you'll need to give it some initial energy and eventually it will start resonating. (See here: http://forums.ni.com/t5/Circuit-Design-Suite-Multisim/Crystal-Oscillator/td-p/1109026)
Usually with a crystal the model is relatively simple. The difficulty with an opamp is that if you give it too much energy (in an effort to get it to ramp up to resonance quickly), the simulation may go nonlinear due to clipping/saturation and the overall simulation at that point may not be reliable.
Please check your circuits again, but perhaps you could try using a thermal noise source + interactive SPDT switch to give it enough of a start (and switch it out if enough energy is applied)? Just an idea... If you see it dampen after the source is off, the phase is likely off.
Master Database -> Signal_Voltage_Sources -> THERMAL_NOISE
Pat Noonan
National Instruments
