Another important frequency related parameter of an op-amp is the slew rate. (Slew rate is the maximum rate of change of output voltage with respect to time. Specified in V/μs).
Reason for Slew rate:
There is usually a capacitor within 0, outside an op-amp oscillation. It is this capacitor which prevents the o/p voltage from fast changing input. The rate at which the volt across the capacitor increases is given by
dVc/dt = I/C --------(1)
I -> Maximum amount furnished by the op-amp to capacitor C. Op-amp should have the either a higher current or small compensating capacitors.
For 741 IC, the maximum internal capacitor charging current is limited to about 15μA. So the slew rate of 741 IC is
SR = dVc/dt |max = Imax/C .
For a sine wave input, the effect of slew rate can be calculated as consider volt follower -> The input is large amp, high frequency sine wave .
If Vs = VmSinwt then output V0 = Vmsinwt . The rate of change of output is given
dV0/dt = Vm w coswt.
The max rate of change of output across when coswt =1
(i.e) SR = dV0/dt |max = wVm.
SR = 2∏fVm
V/s = 2∏fVm v/ms.
Thus the maximum frequency fmax at which we can obtain an undistorted output volt of peak value Vm is given by
fmax (Hz) = Slew rate/6.28 * Vm .
called the full power response. It is maximum frequency of a large amplitude sine wave with which op-amp can have without distortion.
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