I've tried all kinds of methods and keep going back to ICL7660 and=20
variants.

Easily extended to give +12 (+5 x 3 - Several diode drops) and -5V

Also I've used the +V and -V from a 5V driven MAX232. There are versions=20
using 100nF rather than 10uF needed by 7660.
I think there may be a version needing no external capacitors?

With MAX232 you get two inverters that will switch TTL level in/out and=20
two that switch TTL in and +V and -V out.


--=20
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