[sdiy] unused comparators

[David G Dixon]

> On 11/03/2013 04:55 AM, David G Dixon wrote:
> > Yes (based on what Magnus says below), the more I think 
> about it the 
> > more it seems dumb to ground the inputs of an unused 
> comparator, since 
> > the output state will be indeterminate.  Better to connect 
> the rails 
> > to the respective inputs, or one rail and ground at least, and to 
> > arrange it so that the input doesn't consume current.
> Beware, railing them may not be a guarantee for stability. 
> That is a feature of a particular design. Another feature may 
> be that the valid input range may include the rail... such 
> that railing both inputs is just as dumb as grounding them. 
> When you don't know better, park them at distinct levels from 
> each other!
> 
> Just did a quick search for "comparator rail to rail input" 
> and found a bunch of them.
> 
> Cheers,
> Magnus

So, what you're saying is: comparators suck!  Yeah, I concur.  In any case,
if I did have to leave one unused (which I don't), I would hook the inputs
up to +5V and GND.  Since, I'm running some TTL off them anyway, I have a 5V
source in the circuit, so yeah.  I wouldn't hook it up to the rails.