Linear JFET instead of dual gang pot?

Discussion in 'The Projects Forum' started by krabbacitor, Aug 17, 2011.

  1. krabbacitor

    Thread Starter New Member

    Oct 21, 2009
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    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
     
  2. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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  3. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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  4. MrChips

    Moderator

    Oct 2, 2009
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    You will have a problem matching the two FETs exactly. Depending on your situation digital pots may be a possible solution.
     
  5. Audioguru

    New Member

    Dec 20, 2007
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    Jfets used as a resistor (in AGC circuits or oscillators) produce distortion unless the level to them is very small.
     
  6. studiot

    AAC Fanatic!

    Nov 9, 2007
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    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.
     
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