Micro-Theremin IC

Don Duval donduval at mindspring.com
Fri Mar 13 00:07:55 CET 1998

(Please excuse me if this message is a repeat. As near as I could tell, the
original message did not get sent.)

media at mail1.nai.net wrote:

>...material deleted for brevity...

> More peculiar is that only half of the NAND's on each chip are used. 
> The
> notes say "4093 pins 2,6,14 = +15v,  7,8,9,12,13 = ground."  It makes
> no
> mention of the outputs of the two unused NAND's (pins 10, 11).  I can
> only
> assume they are also tied to ground -- from everything I heard CMOS
> circuits shouldn't have unused pins.

There is no problem in leaving the output pins unconnected. In fact, it
is better that you do *not* connect the output pins to either ground or
+15v. Doing so is likely to cause the part to fail, unless you are
careful that you connect to the voltage which the output is "trying" to
reach due to the logic levels on the input pins. Basically, there is no
benefit to connecting unused output pins to any particular voltage level
in CMOS circuits.

All input pins, on the other hand, should be connected to either logic 0
or logic 1. In the case of the circuit you have described, logic 0 is
equal to 0 volts (aka ground) and logic 1 is equal to 15 volts. As
others have mentioned, in other CMOS logic families, the logic 1 may be

> ... more stuff deleted for more brevity...
> Where did you find this Micro-theremin circuit??  I'd like to take a
> look
> at it.

I'd like to see it, too.

from a former lurker,

Don Duval

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