[sdiy] CMOS schmitt trigger question

[harry]

media at mail1.nai.net wrote:

> I've heard you can run various CMOS chips without connecting power to Vdd!!
> (not that it's a good idea)
>
there are two cases... one where you deliberately play with the power... such
as
the 4049 hex VCA trick (uses 6 n-mos transistors in the package)

The other is if you forget to connect Vdd or Vss... and one input pin happens
to
be high (or low as the case may be)... the chip will suck its own power through
the
forward biased input protection diode.

This can be a BITCH to find... as the circuit may seem to work perfectly...
until
the state where that input goes away...  (been there..)

Its not usually a good idea to not apply power and ground.

H^) harry

>
>

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