Tremolo Circuits - The Oscillator

This video is about the circuit analysis, of the oscillator used, in guitar amplifier tremolo circuits. It’s a very simple resistor/capacitor phase shift oscillator. Despite its simplicity, the circuit analysis is somewhat rigorous. We will be doing a derivation, of the equations for the oscillator frequency, and the required gain of the amplifier.

At 9:58, the factoring out of j should have been factoring out 1/j.


00:00 Intro
00:34 Tremolo vs. Vibrato
01:19 Fender Vibrolux Vibrato Circuit Schematic
03:36 RC High Pass Filter
04:47 Control Theory Model of Positive Feedback - Barkhausen Criterion
06:49 3-Stage RC High Pass Filter Analysis
11:20 Transfer Function
12:12 Speed/Frequency Control
13:56 Nonlinearity of Speed Control
14:38 Opamp RC Phase Shift Oscillator
15:36 Lab Demo