[sdiy] cmos 555 r divider values

[Neil Johnson]

> I am sure there is a good reason for it. But why-oh-why didn't they put a
> complimentary output on a 555?????

I guess 9-pin DIPs were not so popular then?

> I mean, there must be a billion or so 555s with pin 5 bypassed by a cap
> and a NPN transistor inverter attached to make a Q NOT output...

That pin 5 can be used to modulate the osc frequency, ideal for simple FM
applications.  I think that what he did come up with lasted so well
because it works for many, many different applications.  An output that
can sink or source 200mA can do an awful lot (DC-DC converter, drive
relays or lamps, etc).

If there are a billion 555s needing a complementary output, there are
probably several billion more where the complementary output would be
wasted and the lost functionality would be a right PITA.

Neil

--
Neil Johnson :: Computer Laboratory :: University of Cambridge ::
http://www.njohnson.co.uk          http://www.cl.cam.ac.uk/~nej22
----  IEE Cambridge Branch: http://www.iee-cambridge.org.uk  ----