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LM387N replacement OP AMP

Robert Thompson1
Prodigy 10 points

Other Parts Discussed in Thread: LM837

The LM387N has been obsoleted. What would be a good, or better, OP AMP for use in a circuit designed for the LM387N, even if the pinout is different? The main concern is that the circuit itself should need no changing with the replacement. This is an audio circuit. Any suggestions would be appreciated. Thank you.

  • 0
    TI__Guru 70156 points

    Hi Robert,

    The LM387 is basically a dual 15MHz, 7nV/Hz op-amp with special self-biasing (Vs/2) output.to allow direct AC coupling to the inputs without using external bias resistors. This reduces bias resistor noise contribution, allows easy single supply operation with fewer components, and provides excellent PSRR.

    "Normal" op-amps require a DC path to both inputs to set the output reference.

    You will notice in the example schematics that the LM387 non-inverting inputs are AC coupled and do not require Vs/2 bias resistors. However, there must be a DC path between the output and the negative input to maintain DC feedback.

    Most of the typical applications shown on the datasheet can be duplicated with "normal" op-amps, but DC biasing will need to be added.

    You may have to modify your existing circuit a bit by adding a blocking cap or a few bias resistors to use a "normal" op-amp. The LM837 has a different pin-out not normally used with dual op-amps - so any board layouts would have to change.

    Regards,