[sdiy] In search of a reasonably precise comparator output

[Guy McCusker]

Thank you.

I can readily stick a solid 5V reference on the pull-up of an
open-collector or open-drain comparator, but I am feeling stupid about what
happens for the low output voltage. The LM339 data sheet lists a V_OL of
150 to 400mV. That's a reasonable way above 0V.

Should I just live with it and trim it somewhere else in the circuit?

Guy.




On Wed, 20 Jun 2018 at 17:02, Pete Hartman <pete.hartman at gmail.com> wrote:

> On Wed, Jun 20, 2018 at 10:30 AM, Lloyd Abbott <lloydabbott94 at gmail.com>
> wrote:
>
>> What rails do you have available ? Have you considered a comparator IC
>> (e.g. LM339) rather than using general purpose op-amps ?
>>
>> If you have 0V, +5V and +15V rails, with an LM339 you can reference the
>> comparator input side to the 0V and +15V rails and have the output side
>> referenced to 0V and +5V. The datasheet has an example circuit using one
>> pullup resistor and one cap per comparator.
>>
>>
>
> I was going to suggest this as well.  The 339 and its family are all open
> collector outputs, so you can use a pull up to any voltage you like, a rail
> or a reference voltage or whatever to get the swing you need and if
> necessary convert levels.
>
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