[sdiy] In search of a reasonably precise comparator output

mark verbos markverbos at gmail.com
Thu Jun 21 11:06:31 CEST 2018


Guy,

A friend and I worked out ideas for exactly this kind of thing a week or two ago. In waveshaper circuits, where you need the comparator outputs to be very accurate, the pull up might be a problem. What about a rail to rail opamp powered from 0 and +5? You can make the pull up very small compared to the input resistor to the summing stage, but it can never be perfectly symmetrical. 

Mark




> On Jun 20, 2018, at 5:05 PM, Guy McCusker <guy.mccusker at gmail.com> wrote:
> 
> Hello,
> I am "designing" (i.e. cobbling together) a circuit in which I need a
> comparator whose output is fairly accurately 0V or 5V.
> 
> I can think of many ways to do this. Some are very stable (at least on
> paper) but appallingly complicated, which is bad because I need at
> least 7 of these;  some are very simple but rely on careful trimming
> of the saturation voltage of an op amp, which I would rather not do
> for reasons of reproducibility.
> 
> It is 100% likely that someone on this list has a very simple and
> solid way to do this, so rather than reinvent the wheel I thought I'd
> ask... how would you do it?
> 
> (What I really want, in fact, is to take an input voltage X and output
> X if X<=5, or X-5, if X>5.)
> 
> Guy.
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