[sdiy] CMOS for linear circuits.

[Roy J. Tellason]

On Thursday 03 November 2005 10:46 pm, ryan williams wrote:
> hi all,
>
> since I'm currently building some cmos filters, vcos, and theremin
> control circuits I have been wondering about using multiple gates on the
> same part.
>
> the glasgow theremin
> http://home.att.net/~theremin1/Glasgow/glasgow.html
> uses all CMOS to generate a control voltage from hand-antenna distance
> (just like any other theremin, but with tachometer). They have used a
> different IC for each gate that sees a frequency that is different from
> the others. There is 10 ICs total just to make up the antenna->CV
> sections. there are enough available gates to do this with only 5 ICs.
>
> Whats the deal with this. I expect there might be some coupling between
> gates on the same chip? I have not experienced something like this but
> only read people mentioning that kind of problem. So when is it ok to
> put them on the same chip, and when should they be seperate? maybe it's
> a complicated question. if so, what books to read?

The problem with operating CMOS gates in linear mode is that power dissipation 
goes WAY up from other modes of operation,  this may be a factor with the 
design you're looking at.

As far as books go,  see if you can find a copy of Don Lancaster's CMOS 
Cookbook,  highly recommended for anybody messing with this stuff.

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