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.

http://www.simplecircuitdiagram.com/wp-content/uploads/2010/10/Basic-Phase-Shift-Oscillator-1KHz.gif

Ignore the opamp circuit.

[Garengineer]

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

http://www.simplecircuitdiagram.com/wp-content/uploads/2010/10/Basic-Phase-Shift-Oscillator-1KHz.gif

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/%7Edoncox/wec/Oscillators.html