# "Is voltage equal to" curcuit

#### bok

Joined May 7, 2010
2
Hi.

I have a signal that ranges between 0 and 5 volt, and i need to design a curcuit that outputs a logic 1 if this voltage is equal to 2.4V.
The tolerance is +-0.5 volt.

I been trying to crack this for a while, but cant seem to figure it out, anyone got any idea ow to accomplish this?

Bok

#### GopherT

Joined Nov 23, 2012
8,009
Hi.

I have a signal that ranges between 0 and 5 volt, and i need to design a curcuit that outputs a logic 1 if this voltage is equal to 2.4V.
The tolerance is +-0.5 volt.

I been trying to crack this for a while, but cant seem to figure it out, anyone got any idea ow to accomplish this?

Bok

Google "comparitor" or "window comparitor" if the lower value is also important. That is, if you also want a logic 1 if voltage is below 1.9V (not in your 2.4V range).

Also, you may want to discuss/post schematics if what you've tried and failed with so far.

bok

#### bok

Joined May 7, 2010
2
Perfekt! The window comparitor is exactly what i am looking for.

#### MikeML

Joined Oct 2, 2009
5,444
Or a single comparitor with hysteresis, sometimes called a Schmitt Trigger.

For example, output become 1 when input exceeds 2.45V but the input has to decrease below 2.35V for the output to go back to 0. Such a comparitor would have a hysteresis of (2.45-2.35) = 100mV.

Here is an example. The Reference voltage can be derived with a voltage divider from V(dd). It requires an OpAmp or Comparitor chip that has a full-swing output of 0V to V(dd).

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