[sdiy] CMOS Synth

[Magnus Danielson]

From: harrybissell <harrybissell at prodigy.net>
Subject: Re: [sdiy] CMOS Synth
Date: Mon, 03 Feb 2003 00:12:20 -0500

> Why not try the CD4007... where you could use "emitter resistors"
> (well I know they are not emitters... but I mean like in the output
> stage of a bipolar audio power amp.

If you *really* think about it (I know it is hard) emitters is best understood
as a word when thinking about tubes, ain't it? Collector is equalently obvious
then, ain't it? Both NPN-transistors and N-channel FETs have the correct
directions for electrons in this analogy. In a similar sense is both source
and drain (source of electrons and the drain down which used electron goes)
equalently obvious, ain't it?

So if you *really* think of it (instead of just nitpicking about conventions)
where you using it incorrectly?

No. ;O)

In tubes it's so obvious where the electron goes. The irony in it all is that
I can never recall which is the anode and which is the cathode... but gate I
darn well understan... if you open the gate, you can go though... right ;O)

> These could limit the 'shoot through' current to a manageable level,
> allow the output to still be centered in the supply range... and not
> cause all the devices in the package to be unfortunatly coupled as in
> the case of resistors in the power supply legs.
> 
> The inverter in the 4007 could not use this method...

You are correct in that 4007 is better since it allows access to individual
transistors even if they sit on the same chip. However, if you leave your
ordinary engineering sense behind and think about geeky odd-ball solutions, you
realize that the 4069UB is the optimum since it is a digital gate which allows
all kinds of analogue tweaks. So, there's the motivation for the challenge, to
use all kinds of ways to bend the digital gate to do quite usefull analogue
properties. The challenge of creating a full synth with no other active
components than the 4069 is there not for the extreme high quality aspect of it
but there for the mindbending needed and challenge of getting decent
performance out of a "dead matter" as digital gates can be.

So, yes, the 4007 is to some degree more optimum, but is it as much fun?

Cheers,
Magnus