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OPA197: Short Circuit Current much lower than stated

Henrique Matos
Prodigy 20 points
Part Number: OPA197
Other Parts Discussed in Thread: OPA1622

Hi, i'm working with a OPA197 outputting a sine wave centered in zero with 1.76Vp , ie, 1.250 Vrms. The amplifier is powered with +-3.3V and i was expecting to get something close to a maximum source current of a Irms= 46mA (65mA peak as stated in the datasheet) but it turns out if i put a load that forces a current higher than 30mA, the amplifier doesn't provide it and it starts to clip the wave. Am i missing something ? Thank you. 

  • 0
    TI__Mastermind 23050 points

    Hi Henrique,

    The amplifier may be able to source 65mA, but not at full output swing. As you increase the output current, you effectively lose headroom in your output voltage.The following figure depicts this behavior: 

    A 1.76V output signal puts you 1.54V away from the positive supply. If you look at the curve for 25C, you will notice that at (V+) - 1.54 you intersect the claw curve at approximately 30mA. The OPA197 can only source more current by limiting the output voltage, which is why you see clipping. The section where the curve drops off represents the short circuit current of the device. 

    Regards,

    Zak Kaye

  • 0 in reply to Zak Kaye
    Prodigy 20 points
    Hey Zak Kaye, thank you very for your answer, makes sense. I was trying to find an opamp that would provide me the 65mA with this headroom, but i can't find any, mostly because a lot of them don't have a figure like this. Do you have any suggestion ? Thank you.
  • 0 in reply to Henrique Matos
    TI__Mastermind 23050 points
    Henrique,

    It is hard to make the best recommendation without knowing more about your requirements, but based on what you've said I would suggest looking at the OPA1622. This part can accommodate your supplies and should be able to source 1.76V at 65mA.

    Regards,
    Zak Kaye