Hi there!

Since precise dual ganged pots are rather expensive, I asked myself if it would be possible to replace them when needed (for example in a wien bridge oscillator) with JFETs working in the linear region, eg. as variable resistors, controlled at the gate via a single potentiometer?
I'm just a DIYer and a rookie, so I'd actually rather solder some small circuit with cheaper components that I've available than to pay a lot money for some dual gang pots which are clumsy and could maybe be replaced by a trim pot...
Does anyone have any advice? I tried googling for some time but seemed to miss the right words...

Thanks
Christian

 

http://users.ece.gatech.edu/~lanterma/sdiy/datasheets/transistors/vishay_fet_cvr_an.pdf

 

http://users.ece.gatech.edu/~lanterma/sdiy/datasheets/transistors/vcr2n4n7n.pdf

 

You will have a problem matching the two FETs exactly. Depending on your situation digital pots may be a possible solution.

 

Jfets used as a resistor (in AGC circuits or oscillators) produce distortion unless the level to them is very small.

 

If you want to uses FETs you would better to employ them for their high impedance in an amplifier so you can use a ganged variable capacitor instead of a pot in your Wein oscillator. These are more reliable, cheaper and easier for an amateur to come by.