Phase Shift Oscillator Question

Click For Summary

Discussion Overview

The discussion revolves around the construction of a phase shift oscillator using transistor amplifiers, specifically BJT or MOSFET types. Participants explore the requirements for the amplifier and the feedback network necessary for oscillation, comparing it to traditional op-amp designs.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant notes that a phase shift oscillator can be built using a transistor and a few components, suggesting that the op-amp circuit can be ignored.
  • Another participant questions whether any type of transistor amplifier can be used as long as it provides some voltage gain.
  • A different participant asserts that achieving oscillation requires a minimum gain of 27, indicating that a high gain transistor is necessary and that specific components must be followed closely.
  • A participant shares an image of a BJT circuit with a four-stage phase shift network and references a formula for a three-stage network, providing a link to additional design resources.

Areas of Agreement / Disagreement

There is no clear consensus on whether any transistor amplifier can be used for the phase shift oscillator. Some participants suggest that specific gain requirements and component choices are critical, while others propose a more flexible approach.

Contextual Notes

Participants express differing views on the necessary gain for oscillation and the types of amplifiers that can be utilized, indicating potential limitations in assumptions about component compatibility and design specifics.

Garengineer
Messages
4
Reaction score
0
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?
 
Engineering news on Phys.org
You can make a phase shift oscillator using one transistor and a few components.

Basic-Phase-Shift-Oscillator-1KHz.gif


Ignore the opamp circuit.
 
vk6kro said:
You can make a phase shift oscillator using one transistor and a few components.

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?
 
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.
 

Similar threads

  • · Replies 27 ·
Replies
27
Views
3K
  • · Replies 41 ·
2
Replies
41
Views
8K
Replies
33
Views
6K
  • · Replies 6 ·
Replies
6
Views
3K
Replies
2
Views
2K
  • · Replies 1 ·
Replies
1
Views
1K
  • · Replies 3 ·
Replies
3
Views
3K
  • · Replies 46 ·
2
Replies
46
Views
6K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 1 ·
Replies
1
Views
4K