Using a Comparator As an Inverter

About: Electrical Engineer, control systems, automation, small electronics, home automation, microcontrollers etc.

When you've got some comparators either already in your circuit or built into your MCU, there are some handy tricks you can use.  The following will show you how you can use a comparator to make a Logic Inverter.

Your signal will be sent to the inverting input of the comparator (negative terminal).  The non-inverting (positive terminal) will be connected to a voltage divider to provide V+/2 using two identical resistors.  The values of R1 and R2 are not set in stone, you can adjust them as long as they are both the same value.

So now, when the input is below the positive terminal's value (V+/2), the output will be V+ (high).  When the input is above the positive terminal's value (V+/2), the output will be 0 V (Low)

And that's it



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    2 Discussions


    4 years ago on Introduction

    Why can't you use different valued resistors and compare at a different voltage level?

    You'd still get V+ and 0 out, right?

    1 reply

    Reply 4 years ago on Introduction

    Correct, you could use any resistors you would like. The switching point of the output will be the voltage seen at the + terminal of the comparator, so if both resistors are the same value the output will switch at 1/2 V+.