Phase Shift Oscillator Question

[Garengineer]

Hello everyone. I understand that a phase shift oscillator works by connecting an amplifier through a feedback network that shifts the input by 180 degrees. Although I remembered building a phase shift oscillator in my circuits class using an omp amp, I would like to build one using a bjt transistor or a mosfet amplifier. Will any transistor amplifier work with a phase shift oscillator, or do you have to use a certain amplifier?

 

[vk6kro]

You can make a phase shift oscillator using one transistor and a few components.

Ignore the opamp circuit.

 

[Garengineer]

You can make a phase shift oscillator using one transistor and a few components.

Ignore the opamp circuit.

So it does not matter which type of transistor amplifier it is for the phase shift network as long as it has some voltage gain?

 

[vk6kro]

No, these are quite tricky to get going. I recall you need a gain of 27 minimum for the circuit to oscillate.

So, the transistor needs to be a high gain type and you should follow the components described exactly.

 

[The Electrician]

The image shows a BJT circuit with a 4 stage phase shift network. The formula shown is for a 3 stage network.

This page will help you with the design of a BJT phase shift oscillator:

http://home.earthlink.net/~doncox/wec/Oscillators.html