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Original question:

[FAQ]High Speed Amplifier Application Notes

OPA209: High Speed Amplifier Application Notes

Sreehari kamsala
Prodigy 90 points

Part Number: OPA209

For Op Amps made of BJT, we are using an resistive circuit for input bias current cancellation. Which kind of method is used to cancel the input bias current for an Op Amp made of CMOS? 

Kindly please answer....

Thanks in advance....

  • 0
    Guru 140200 points
    Hi Sreehari,

    CMOS OPAmps usually have only very little input bias currents. Then a bias cancelation resistor is not needed.

    Kai
  • 0 in reply to kai klaas69
    Prodigy 90 points

    Hai kai klaas69

    Thanks for your response,

    But my question is how to reduce that bias currents further. Is there any method or any trick to make it still less.

    Any kind of suggestions are appreciated.

    Sreehari

  • 0 in reply to Sreehari kamsala
    Guru 140200 points
    Hi Sreehari,

    the usual input bias current cancelation method does not reduce the input bias currents. It only makes that equal voltage drops are generated at both OPAmp inputs and by this no additional offset voltage is produced. Concretely spoken, two identical offset voltages are generated at each OPAmp input which cancel each other by the operation of OPAmp. Remember, an OPAmp amplifies the voltage difference between the two inputs.

    Kai