[sdiy] Which is better as a VC resistor? FET or BJT?

Tom Wiltshire tom at electricdruid.net
Thu Jun 30 18:05:05 CEST 2011


There's plenty of FET phaser schematics flying about that use them as Harry suggests, from some node to ground. Maybe you could pick up a few ideas there. Secondly, didn't the old Boss pedals use FETs for the noiseless bypass switching (whch seemed really cool back in the day - now everyone wants 'true bypass' with big clunky switches!). Again, there are loads of schematics for those on the web.

T.

On 30 Jun 2011, at 16:07, Harry Bissell wrote:

> 
> There was an old siliconix app note about using FETs a voltage controlled resistors.  Maybe you can find it on the web
> at Vishay Siliconix. In general they work best in shunt applications (the resistance is from some node to ground.
> 
> Osamu Hoshuyama had some examples in his webpages, something about tuning filters and the methods used (non-linearized, linearized, etc)
> 
> H^) harry
> 
> 
> 
> 
> ----- Original Message -----
> From: dan snazelle <subjectivity at hotmail.com>
> To: Synth DIY <synth-diy at dropmix.xs4all.nl>
> Sent: Thu, 30 Jun 2011 11:00:49 -0400 (EDT)
> Subject: [sdiy] Which is better as a VC resistor? FET or BJT?
> 
> I am messing around with a new circuit where I want to voltage control the path between two points. I was using a BJT last night but was getting  a lot of distortion (maybe i need to find more info on proper use of BJT's as
> VC resistors)...maybe a FET would work better?
> 
> any opinions on FET vs BJT?
> 
> any advice on good articles/books that cover this topic?
> 
> thanks!!!!!
> 
> 
> 
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> -- 
> Harry Bissell & Nora Abdullah 4eva
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