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50hz AC 20mV pk-pk to Square wave (Zero Crossing Detector) using OPA379 single supply opamp

Other Parts Discussed in Thread: OPA379, LPV7215

I am using OPA379 Single supply ultra low power opamp for SIne to Square wave converter...(ZERO CROSSING DETECTOR)

Input is 20mV pk-pk AC Sine wave from Current Transformer..

Supply voltage is 3.6V battery...

I want to design precision Zero crossing Detector using OPA379 opamp..

Can any body suggest me any Design Technique..

  • Ravi,

    Op amps are NOT best suited to be used for zero-crossing detector due to its relatively low slew rate and long overload recovery time (output coming out of rail).

    In the case of OPA379, not only the typical slew rate is just 0.03V/us but more importantly the typical overload recovery time is 25us greatly limiting the maximum detection speed - see below.

    It would be much better in your application to use one of the our comparators like micro-power LPV7215 with IQ of less than 1uA and the speed much greater than any op amps with similar quiescent current may ever be - see attached.

    Zero Crossing detection Methods.pdf
  • Thank you Marek,  

    Attachment is really very useful for my application...

    Thanks again...