Created by
Created December 29, 2012
Last modified January 21, 2013
Tags bridged-t   oscillator  


A unique oscillator circuit with simple AGC.


A traditional oscillator is made of a frequency defining circuit, amplifying it,
and providing enough "Positive Feedback", to create & sustain oscillations.

Not so with this oscillator;
"Positive Feedback" provides "Fundamental Frequency + Distortion", through R1.
"Negative Feedback" provides "Distortion" only, through a "Bridged-T" filter,
which has removed only the "Fundamental Frequency", and passes all the "Distortion".
The "Amplifier" rejects the "Common Mode" "Distortion", amplifying the "Fundamental" difference.

Feedback amplification is ((R1+R2)/R1).
Set to a minimum helps reduce "Clipping Distortion".
Gain control is provided by D1, D2, + R3 "Clipper", shunting R2.

This circuit design should provide low distortion.


I cannot make this work.It seems to me that the amplification is 1.20 whereas I would expect slightly more than 3.0

by Edalamram
February 04, 2016

Does this circuit actually operate? Is it possible that R2 should be 21.2k? I am attempting to convert a Heathkit vacuum tube audio generator to solid-state components in order to save heat. I would appreciate a reply. Edalamram

by Edalamram
February 09, 2016

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