Unused CMOS inputs

[Toby Paddock]

The way I understand it, floating inputs can, umm, float around.
One thing I found out when I was using cmos 
schmitt inverters as touch switches is that when an 
input is "somewhere in the middle" the chip will 
draw current.
(old fuzzy memory, I hope it's right)

Another thing I found by accident is that a floating 
cmos input with a few inches of wire makes an 
electrostatic field detector.  Very very high input Z.  
I had an (non schmitt) inverter driving a LED. 
The input was floating with a piece of wire hanging out.  
As I moved my hand or scuffed my shoe on the 
floor the LED would change brightness. 
Might not work with buffered chips(?)

Sorry, I don't think I answered the question.

 - -- -  Toby Paddock
http://www.seanet.com/~tpaddock

Chris MacDonald wrote:

>I have read that it is good practice to ground unused 
>CMOS inputs to prevent unintended behaviors.  
>Is it also acceptable to set them to V+ or
>V-?  This would be really convenient when not using the 
>buffers in the LM13700 for instance.

>Thanks,
>-Chris MacDonald