Why is opamp slew rate specified at unity gain?

Dear Team,

May I know why Opamp slew rate is defined at unity gain.

Can we say there is no relation between Slew rate and gain.

I know that slew rate depends on the Iq and Cc,but in the case of op-amp if we increase the Iq then there will be decrease in the gain.
if u decrease the Iq then gain will increase.(rds=1/lambda*Id) gain of the op-amp=gain1st stage * gain2ndstage

Regards

Hari

  • Hari,

    I think you are getting two things mixed up.  If you model an op amp as a transconductance stage driving an integrator,

    then SR is a function of Iq and Cc.  But the output stage might be a dog, and the sr would be less.

    SR on the data sheet is for the whole part.  

    We could always spec sr at a gain of -5 or +10 or whatever, but for 40 years, it's been a gain of +1, so we can compare

    op amps over the ages.

    Harry

    PS  " if we increase the Iq then there will be decrease in the gain."  What about a bipolar?  We do make op amps w/ BJTs.....