Quenching circuit

Hey,

Can anyone tell me what's the usage of a quenching circuit in superregenarative receiver? What happen when we change the quenching voltage?

Thanks
Charis

Well, superregen is a strange beast indeed. Lets say you had a transistor that had 20 dB of gain at your RF frequency of interest. It will boost up a weak signal by 20 dB, nothing more, nothing less, if it is used as a linear amplifier.

However, if you set up that same transistor with positive feedback, it will, for a brief period of time, have a very high (theoretically infinite) gain, due to the feedback. The only problem is that a few milliseconds later, due to this high feedback, it starts to oscillate. Once it is oscillating, is can no longer act as a high gain amplifier.

So one can add a quenching circuit that shuts off the transistor just before it bursts into self oscillation. Thus, with one transistor, one could get maybe 70 dB of gain.

And yes, the waveshape and voltage of the quenching circuit is important for proper operation, and must be tweaked.

Hi biff

Please correct me if i'm wrong, so the quenching circuit is just to provide more gain to the rf signal, as well as tweaking the voltage of the quenching circuit.

How is the quenching circuit connected in the superregenarative receiver? Is it providing the quenching signal to the oscillator?

By the way, what's the parameters of the quenching circuits that should i be looking for?

Thanks in advance
Charis

This might explain better. http://www.eix.co.uk/Articles/Radio/Welcome.htm