Unused IC inputs

[Magnus Danielson]

From: Harry Bissell <harrybissell at prodigy.net>
Subject: Re: Unused IC inputs
Date: Sat, 29 Jul 2000 16:49:16 -0400

> Re: 4049
> 
> You usually "can" parallel gates IN THE VERY SAME IC PACKAGE  !!!!
> Do NOT parallel gayes in different packages !!! They will not be matched.
> 
> In a digital circuit, paralleling gates will double the input capacitance, and
> double the
> output drive current. A two-edged sword, you get more current for possibly an
> increase in
> output speed... vs the input will require twice the current to reach the same
> speed.

Yes, but used correctly you can acheive the required output current with
minimum delay but parallelling inverters and then put parallelled versions in
series... for each stage you have n times more inverters in parallell than the
stage before. Often n is 3 or 4 which yields the best result. This is what
chipmakes do occasionally on small geometries CMOS. But then, we are talking
stompboxes here and not chip making ;)

> If you send me / refer me to the schematic I could be more specific.

Generically true, I too would like to see ;)

Cheers,
Magnus