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op amp buffer current gain equation...

Dai Vu96212
Prodigy 50 points


a voltage gain for an op amp buffer configuration is 1.  What is the current gain for a buffer - more specifically what is the equation for calculating the current gain?

  • 0
    TI__Guru* 93105 points

    Hi Dai Vui,

    An operational amplifier, connected as a buffer amplifier, is a voltage amplifier with a gain of +1 V/V. It is not normally specified in terms of a current gain (A/A). I suppose if one did have a reason to define a current gain for the amplifier then it would be a measure of the change in output current, divided by the change in non-inverting input current. The input current would be a function of the type of amplifier input stage used, bipolar, JFET, or MOSFET, and how its input bias current changes with the changing common-mode input voltage (the voltage at the non-inverting input). The output current change will be a function of the output voltage swing being developed across its load impedance. For example, if the output current was changing 1 mA for an input current change of 1 pA, then the current gain would be 10-3A/10-12A, or 109 A/A. Do note that this would be a highly unconventional specification for the buffer amplifier and of questionable value.

    Regards, Thomas

    PA - Linear Applications Engineering