[sdiy] A bit odd FET question maybe

[Magnus Danielson]

From: "Theo" <t.hogers at home.nl>
Subject: [sdiy] A bit odd FET question maybe
Date: Sun, 18 Jul 2004 12:18:30 +0200
Message-ID: <001401c46cb0$9302e1a0$93b37ad9 at ensch1.ov.home.nl>

> Hi guys,
> 
> Please have a good laugh, but I just have to ask some silly things in even
> more silly non EE speak.
> 
> Like a FET (N, not enhanced, not TTL compatible, ect) is similar to a Triode
> tube,
> do there exist FET with more than one gate similar to Thetrode or Pentode?

There exists dual gate FETs. They are used in RF mixers mainly, for the obvious
reasons. 

> Would a kind of cascode stack of two FET give a similar result?

Not quite, but it may very well work for you anyway.

> I am thinking a minimalist VCA build from two FET set up like a anode
> follower.
> And hope to get less distortion  than with the usual setups.
> 
> V+ -> R"anode" -> D1...S1 -> D2...S2 -> R "cathode" -> ground.
> 
> R"anode" is where the signal is taken.
> R"cathode" is to make S2 positive against G2.
> Maybe a fixed bias to G2 and S2 directly to ground would be better.
> Signal goes to G2,
> CV goes to G1.
> FET 1 would act as VCR controlling the "anode" current trough both FET and
> therefore the amplification.
> 
> Does this make sense or is it just a silly case of doing things in a stupid
> way?

Try it and let us know how it went. People fiddle around to little with 
transistor these days. At one time synth-DIY where transistors and coils much
more than today.

You might want to consider mixed FET and BJTs.

Cheers,
Magnus