- Joined Mar 17, 2017
Simulators normally do a DC bias calculation before doing a transient analysis, which can put an oscillator circuit in a quasi-stable DC state with no oscillation.
Normally circuit noise would start the oscillation but the simulator has no noise so you have to start the oscillation by some other means.
One way is the use the .ic command which avoids the DC calculation before the Transient analysis.
Another is to add a voltage source in series with the feedback loop and have it output a single small pulse at startup.
After the pulse, the voltage source looks like a short-circuit and has no effect on the circuit's operation.
When I changed R5(Rf) to 70k I got the result. As I understood from above answers R1 alone must be used. Then, what is the equivalent of R1 and R4.I see two possible problems:
- The old 741, may not be fast enough for the chosen frequency, or it can not supply enough current to the feedback network.
- The final phase shift is formed by R1 / C1, then R4 must be removed.
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by Jake Hertz
by Steve Arar