Archive of the former Yahoo!Groups mailing list: MOTM

The usual practice is to have an electrolytic cap and ferrite for
each power supply "rail" as close as possible to where the power
supply voltages enter the circuit board. For MOTM stuff the
electrolytic cap of choice seems to be a 10uF 50V. If your circuit
draws a lot of power you might consider a larger value such as 33uF
or 50uF. In addition it is a good practice to liberally sprinkle
bypass caps throughout the circuit board. The MOTM choice is
a .01uF axial cap. There should generally be at least 1 bypass cap
for each power supply voltage every other IC chip, located as close
as possible to the chip. Some people prefer to use more some less.
The idea is just to keep noise off the power supply lines, and
possibly to prevent parasitic oscillation as well. There are even
some IC sockets available with the bypass caps built in but when
using these it is important to make sure the power supply pins on
your IC chips match the location of the cap built into the socket.
If your circuit includes additional voltage regulators you would
want to have an electrolytic cap and ferrite on the output of each
regulator as well.