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LMH6654: Input Offset compensation for open loop configuration

Anthony Mwila
Prodigy 50 points
Part Number: LMH6654

I'm using the LMH6654  as a comparator for a project and I was wondering how to compensate for input offset in a circuit that uses the op amp in open loop configuration. All the solutions I come across provide only closed loop solutions.

  • 0
    TI__Genius 14036 points
    Hi Anthony,

    In general, high speed op amps don't make good comparators since they are not optimized to operate continuously at their output rails, and may even be damaged. While there is not really a way to eliminate offset voltage, for a single op amp in a project, you could directly measure your amp's specific offset voltage and calibrate it out by modifying your bias resistors. However, offset is typically a small enough percentage of the comparison level that it is ignored.

    Best regards,

    Sean
  • 0 in reply to Sean Cashin
    Prodigy 50 points
    Just another question concerning the LMH6654 , I see that the voltage allowed on the input pins is (V+) + 0.5 while the Vin differential is +- 1.2 . does this effectively mean that if I place a 0.5 DC voltage on my non-inverting input anything above 1.2 +0.5 = 1.7 V will possibly damage the OP amp even though the maximum input using a 5V is 5.5V?
  • 0 in reply to Anthony Mwila
    TI__Genius 15975 points

    Hi Anthony,

    Yes. If you place a 0.5V DC voltage on your non-inverting input, then anything above 1.7V (or -0.7V on +/-2.5V supplies) on the inverting input will possibly damage the op-amp even though the maximum input using a 5V supply is 5.5V. Or say, if the non-inverting input is at 5.5V DC, then anything below 5.5 - 1.2V = 4.3V on the inverting input might possibly conduct the differential input ESD diodes to damage the inputs.

    Best Regards,

    Rohit