CMOS Buffering Question

[Martin Czech]

> What I'd like your opinions on is what is the simplest way to buffer the
> outputs, ie, protect them from the outside world?
> 
> I've seen several ways to do it - a diode, a transitor emitter follower, a
> CMOS buffer (CD4050), and an opamp buffer.   I'd like to just use the
> diodes, but I'm not sure this is the best way to go.
>
Well ESD is my job, so I can say:  Be carefull with outputs! CMOS or
not doesn't matter. If you carry some charge (a person or tool can
easily charge up to 4000 or even 8000 Volts) and touch the patchcord,
you might blow the input or the output driver.  Junctions are very
sensitive to ESD, as are cmos-gate-oxides. In 99% of the cases I see
every day some junction will blow before the oxide breaks down
(submicron devices).  This may lead not only to sudden malfunction, it
may also show long term effects (slowly rising leakage) which are very
difficult to find.  If it is possible, use some series resistance 100 ~
600 Ohm low inductance carbon or better metal, and behind that 2
clamping diodes (zener) antiparallel  to gnd.  Of course this will slow
down your pulses (slopes) so you have to find the tradeoff between
functionality and security.

On the other hand:  Is it such a bad idea wearing a anti ESD wrist
strap when working with electronic devices, also synths ?

(I recently blew some cmos dsps just carrying them over the backyard an a
dry, sunny day, they where in "secure" conducting foam ... )

m.c.