FET Matching Was: Re: [sdiy] New take on VC moog ladder

[Don Tillman]

   Date: Mon, 31 Dec 2001 14:27:47
   From: Scott Gravenhorst <music.maker at gte.net>

   I'm pretty ignorant about matching FETs.  Any clue 
   for a schematic for a matcher and the methodology?

It depends on the specific circuit.  Sometimes you want to match them
for Idss, sometimes Vgs0, sometimes transconductance at a particular
drain current, it depends, whatever the circuit calls for.  

Does that mean I have to come up with an FET matching circuit for each
FET circuit I design?  Yeah, mostly.  And the test circuit will often
look very simliar to the real circuit.

"Screening" is also a good thing -- FET manufacturing tolerances are
ridiculously wide, so if you want to assure that a circuit will work well
it's often necessary to screen out the FETs with more extreme
parameters.

   Also, what about MOSFETs ?  Same paradigm?  Same matcher?

Yes, same thing.

  -- Don


-- 
Don Tillman
Palo Alto, California, USA
don at till.com
http://www.till.com