AW: PAIA Hex VCA circuit

[BJ]

Magnus Danielson wrote:

> This is exactly how I preceived it. I would feed the input with CV
> through a 100 kohm resistor and also feed the signal into the input
> through a 100 kohm resistor, this way would the N-channel MOSFET be
> linearized. If you do not feed too hot signals on this, it will act in
> the linear region of the FET curve, so it would actually work as well
> as a single FET, but here you got 6 of them wired up for a fairly
> small price. Important not is however that this only works well with
> the unbuffered 4069, the buffered one is not as fun (to say the least).
> 
> It's wild, it's hilarious... got to try just for the sake of it ;)
> 
> Cheers,
> Magnus

Quite interesting this hexa VCA thing, i had a fast 
look into Don Lancaster "filter book" and there is
a short description on how to use "various" things as
a voltage controlled resistor.

One of them is a Mosfet and there Don is suggesting a 1Mohm for feed
back
to get the device more linear, he also mention this about to "rework"
a 4049 to do the same thing but hexa times!

I just had a wery short look at the 4069 as well but 
the input protection diodes may cause troubbles!!

How about using the Vdd pin as an AM modulation input??(Ohh!) ;)

BJ