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maximum output current

Other Parts Discussed in Thread: OPA377, INA210

how to check maximum output current in op-amp when load is cap?

  • Hi Waseem,

    An operational amplifier's maximum output current is controlled by the design. Most often there are data sheet curves that plot output voltage vs. output current as seen below (OPA377). The maximum current will be a function of the supply voltage, temperature and whether the amplifier is sinking, or sourcing, output current. The curves are developed based on dc measurements, but should be close for ac. 

    If you want to check the maximum output current delivered to a capacitor, an oscilloscope current probe is an easy solution. It is essentially a current transformer. The primary, in its case, is the lead coming from the output of the operational amplifier to the capacitive load. Lacking a current probe, a current-shunt monitor IC can be used providing your measurement can tolerate a small added resistance in the current path. Any the current-shunt monitor IC must have sufficient bandwidth for the frequency range beng measured. See the INA210 current-shunt monitor as an example:

    http://www.ti.com/lit/ds/symlink/ina210.pdf

    I mention the INA210, but there may be another TI current-shunt monitor IC that would be a better fit for your measurement setup.

    Regards, Thomas

    PA - Linear Applications Engineering

  • Waseem,

    Output current is also set by slew rate. IOUT = Capacitance * Slew_Rate. (be sure to watch units carefully, Amperes, Farads, and Volts per second).
  • thank u so much thomas:)

  • thank u Ronald:)

    regards
    waseem