Purposeful Signal Gating

[jwpartain1]

Hello! Hope all goes well with everybody here.

I'm trying to put together a circuit block that will essentially act as a noise gate (for instance, ignore all input signals less than or equal to 50 mV p-p, yet pass signals greater than this). In my small experience I've found that under-biasing Ge transistors yields a similar gate effect and I was wondering if this held true with other transistor types as well. I would guess that Si transistors (BJT) behave the same way, but FET types would be a little more linear (I guess is the word) and wouldn't yield the gate effect due to under-biasing.

Any input would be much appreciated!

EDIT: I'm doing some reading regarding threshold voltages and biasing as well. I think this is on the right track.

[mictester]

The problem with this approach is that it will lead to severe distortion, which is probably NOT what you are trying to achieve.

The way that you should consider would be to use an amplifier stage to bring the guitar signal up to a Volt or two. This then drives a diode pump as a rectifier, and charges a capacitor. The charge and discharge paths for the capacitor should be unequal, and have rapid charge, slower discharge. The DC voltage that is derived can then be fed to a comparator. The output of the comparator will change state when the input level exceeds the comparator reference level input. The output of the comparator is then used to operate an audio switch circuit (FET, CMOS switch, transistor switch, etc). Adjusting the setting of the comparator reference will allow a sensitivity setting. There are plenty of simple but effective circuits on the 'net.