Output impedance of an op amp

Discussion in 'Homework Help' started by chungcyk, Mar 19, 2012.

  1. chungcyk

    Thread Starter New Member

    Mar 19, 2012
    1
    0
    I know it is small - but why? I thought it is linked to stage 3 gain, but I thought as a current limiter, it will add to output impedance?

    Thanks in advance :)
     
  2. jtrent

    New Member

    Mar 11, 2012
    26
    4
    Idealy the output impediance is zero. You should take a look at the internal circuity of an op amp to see this.
     
  3. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    The output resistance of an opamp is about 50 ohms to 200 ohms.
    But since it is almost always used with negative feedback then its output impedance at low frequencies is very close to zero ohms.

    If a load tries to change the output voltage then the negative feedback will cause the output voltage to cancel the change by the load.

    The text in the link is WRONG!
     
  4. mlog

    Member

    Feb 11, 2012
    276
    36
    What do you mean by "stage 3 gain" and to what "current limiter" do you refer?
     
  5. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    Yes, opamps have an output current limiter that is usually not operating.
     
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