Unused IC inputs

[Harry Bissell]

Re: 4049

You usually "can" parallel gates IN THE VERY SAME IC PACKAGE  !!!!
Do NOT parallel gayes in different packages !!! They will not be matched.

In a digital circuit, paralleling gates will double the input capacitance, and
double the
output drive current. A two-edged sword, you get more current for possibly an
increase in
output speed... vs the input will require twice the current to reach the same
speed.

If you are using these gates in 'analog' mode... I would NOT parallel them...
I'd worry that you will drastically increase heat and battery drain. Tie the
unused inputs to the -9V terminal (or whatever you tied Vss to...). Leave the
outputs floating

Re: TL072

I would not parallel these at all.  Tie the unused non-inverting input to
'bias' or analog
reference, usually there is a point comming from a voltage divider, or zener
diode reference that is the "virtual ground" of the circuit. Then tie the
unused output to the
inverting input, and nothing else.

If you send me / refer me to the schematic I could be more specific.

H^) harry


Justin Herrmann wrote:

> Hello, list:
>
> I'm building some stompboxes that use two of the six inverters of a CMOS
> 4049 hex inverter chip <http://us.st.com/stonline/books/pdf/docs/2052.pdf>
> and one of the two op-amps in a TL072 jfet op-amp
> <http://sdremote1.njr.com/cdrom/index/ae/ae04010.pdf>.  My question is,
> what do I do with the unused inputs and outputs?  Would I be able to put
> them in parallel with the ones I am using?
>
>                                                 -Thanks-
>                                                 -Justin Herrmann-