Transistors: Phase-Shift Sine Wave Oscillator

RE: Transistors: Phase-Shift Sine Wave Oscillator

DAB — Fri, 20 Jul 2018 19:44:00 GMT

Good post.

It looks like you are definitely overdriving the transistor, so the output graphs are consistent with your saturation issues.

DAB

RE: Transistors: Phase-Shift Sine Wave Oscillator

mcb1 — Fri, 20 Jul 2018 04:22:19 GMT

Nice work on both simulation and real world.

In my mind adding RC filters to a sinewave that will be amplified is going to create filtering of the signal at certain frequencies.

Applying the RC filtering to the feedback is going to affect some frequencies more than others, and therefore to me seems wrong to start with.

However you do need 180 degs inversion to create the oscillation effect.

One question though.

If R2 was shifted from the collector to the supply, would it have a positive or negative affect on the waveforms?

It strikes me that it is also part of the feedback loop, and therefore must be having some influence, although minor because of the value.

Mark

RE: Transistors: Phase-Shift Sine Wave Oscillator

shabaz — Fri, 20 Jul 2018 02:57:58 GMT

Hi Jon,

Excellent blog post and detail : ) It is always fun seeing your oscillators and sound generators.

The technique you mention about breaking the loop and pretending that the oscillator has an input and an output, is something which the world experts on oscillators do : ) There is a nice book by Randy Rhea, although it covers higher frequency oscillators. Anyway, he went on to develop software called Genesys, which was bought up by Agilent/Keysight.

(Link to his books on Amazon).

RE: Transistors: Phase-Shift Sine Wave Oscillator

jw0752 — Thu, 19 Jul 2018 22:33:33 GMT

Hi Jon,

Keep them coming. I will make time to read and learn as long as you have the energy to teach.

John

RE: Transistors: Phase-Shift Sine Wave Oscillator

genebren — Thu, 19 Jul 2018 20:54:47 GMT

Another very interesting blog on analog circuits. Again, your simulations are very close to the actual circuit.

Good work!

Gene