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OPA1612: The lowest resistance that the OPA1612 opamp can drive while remaining stable?

Naser S.
Genius 11605 points
Part Number: OPA1612

My customer is designing an amplifier stage to interface between a measurement amplifier (B&K 2636) and a computer audio interface. The output of the 2636 is typically 500-900mVrms, and the audio interface has an input range of about 5.3Vrms, so they are seeing unacceptably low SNR going into the audio interface.

 

The amplifier stage he is designing needs to be very quiet, and deliver 6 different gain settings determined by a rotary switch that modifies the resistance in the feedback path of the opamp (non-inverting configuration.) He needs to determine what the lowest resistance is that the OPA1612 opamp can drive while remaining stable, so that he may choose the shunt resistor in the feedback path to be as small as possible to minimize noise.

 Regards,

  • 0
    Guru 140200 points
    Hi Naser,

    if you have a look at figure 7...11 of datasheet you can see how the THD-N data varies with different load resistances and frequency. The best performance is achieved if the load resistance is above 2k.

    Kai
  • 0
    TI__Expert 7540 points

    Hi Naser,

    The lowest load resistance we have data for in the datasheet is 600Ω, which should give excellent THD+N performance (better than .0001%THD+N) across the audio band.