wein bridge oscillator

I think you used a lousy old 741 opamp. Its design is 42 years old.
Its output cannot go higher than only 9kHz at full swing.

If you use a better opamp like the TL071 then its output works perfectly up to 100kHz.

need help for orcad simulation

I tried to simulate a circuit diagram of wein bridge in this thread
It simulated error free
but the out put graph is unexpected.
Im very new for orcad.
I know there should be my fault.
plz help.................
orcad 9.2
simulation settings-time domain(Transient) 1000ns

What did you expect to happen in 100e-9 second? It's a 500 Hz oscillator.