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THS4031: Alternative with higher capacitive load drive

Soumyadeep Biswas
Prodigy 50 points
Part Number: THS4031
Other Parts Discussed in Thread: TLC7524, THS3091, THS3491

Tool/software:

Hello, I need an alternative to THS4031ID with similar low settling time and low noise characteristics but with higher capacitive load drive capability. I am using it in inverting configuration with gain of -1.5 at the output of a DAC+OPAMP (TLC7524+THS4031ID) to drive a capacitive load  of about 470 pF. For the TLC7524 DAC in unipolar operation I am using the same THS4031ID to generate 0V to -10V using REF102CU as the +10V reference. This 0V to -10V is being upconverted to 0V to +15V using the second THS4031ID.

I have observed some peaking response at the output load. Then I have used an isolation resistor and feedback compensation capacitor for the second THS4031ID and found the peaking and noise has reduced but the final 0V to +15V settling time has increased considerably. Is there any opamp I can use in place of the second THS4031ID which will not require any compensation or isolation circuit from the capacitive load and thereby retain the same settling time as the DAC ~500-600 ns? Please suggest.

Thank you

  • +1
    TI__Genius 10650 points

    Hi,

    I was able to look over our portfolio for devices that have the extra output drive as this is a larger capacitive load than what is typically highlighted in datasheets and the part that would be worth considering is the THS3091. This is a current feedback device with a larger output current capability which will help with the settling time performance. As far as the option of implementing an amplifier without needing some form of compensation, unfortunately most devices in our portfolio if not all will require some kind of isolation resistor when implementing a capacitive load. For the THS3091, an isolation resistor in the single digits is likely all that is required for this large of a capacitive load.

    Best Regards,

    Ignacio

  • 0 in reply to Ignacio Vazquez Lam1
    Prodigy 50 points

    Hi Ignacio

    Thank you for your suggestion. Will the alternative part THS3491 (higher output current) be a better alternative to THS3091 for this application if I can operate at gain more than 5 in the inverting configuration? Will the higher input-voltage noise matter?

  • 0 in reply to Soumyadeep Biswas
    TI__Genius 10650 points

    Hi,

    The THS3491 could also work for your application and should result in better results as this device has more output drive and is a faster device than the THS3091. The noise performance of these devices is somewhat comparable, so I don't believe it will result in that much of a difference.

    Best regards,

    Ignacio