I have a school project that requires a sine to square wave converter for a sine wave input of 0 - 3.1 V pk from 0Hz to 500kHz. The output must be a square wave with maximum voltage 2.8V - 3.1V. So far I have tried using an op amp as a Schmitt trigger, however the ones I have available cannot work for the frequency range. I have tried the Schmitt trigger using transistors but am unable to get my design to work.

I would appreciate anyone directing me to an appropriate device or any help designing the schmitt trigger.

  • \$\begingroup\$ Here's something(youtube) that will definitely help you out. \$\endgroup\$ Nov 12, 2017 at 7:26
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    \$\begingroup\$ you want a comparator not an op-amp. comparators are designed for logic output. \$\endgroup\$ Nov 12, 2017 at 8:07
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    \$\begingroup\$ How does your circuit look so far? As others said, a comparator would be better. But if you want to learn what you made wrong with the transistors, you need to share your schematic and the results you get from it. How does the output look at a certain input? \$\endgroup\$
    – Grebu
    Nov 12, 2017 at 13:37
  • \$\begingroup\$ @aasif826 if you ask a specific question you'll get better answers. An attempt at a schematic would help \$\endgroup\$
    – Voltage Spike
    Nov 13, 2017 at 4:19

1 Answer 1


Opamps, normally have an output stage that is designed to operate in linear region, to amplify the input without much distortion. On the other hand, comparators are specifically designed to provide a two level output as you need. Select a comparator with high enough slew rate or your output will become triangular. Also if your comparator output stage is open collector, then you will need a pull up resistor.


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