Bypass cap's

[Mark Amundson]

> Steve Varner wrote:
> > Where do you put these in the circuit and what size caps do you use?
> > (5-10 microfarad?)

That question is way easier asked than answered. Even analog engineers
get ruffled by proper use of bypass caps and supply layout issues
(especially ground loops). Here is a couple of my rules of thumb for
circuits a few inches or more from thier power supplies.

1. A cap of about 0.1uf (X7R or Z5U ceramic) is a good choice of analog
IC power supply decoupling (power to ground).

2. If you are dealing with higher frequency stuff as well (like radios,
D/A coverters, etc.) reduce this value to 0.01uf and keep the leads
short and layout tight.

3. Use 10uf to 100uf tantalum or electrolytic caps for local supply sag
issues. Do not use these caps if you have regulated supplies and good
beefy wiring as they may cause more power supply hum than their curative
effects.

Mark Amundson,