CMOS Opamp Slew Rate measurement

[rishabh_31ec]

Hi, I have Designed a 4-stage CMOS Opamp with +/- 0.85 Volt rail to rail supply and obtained the Bandwidth as 4.2 MHz. In order to measure the SLEW-RATE, should I have to apply a step voltage of peak values as ( V+ = 0.85 & V- = -0.85 v ).

I have a confusion regarding width of Step.

I think frequency of Step should be less than Unity Gain Bandwith. Am I right or I can choose any frequency of Step.

 

[KlausST]

Hi,

One hint is to look into datashhets of opamps and to see how the manufacturerst test this.

Voltage level: I expect different slew rate depending on input levels. With large voltage and high dV/dt the input stage may be overdriven causing varying slew rate.

Hope this helps
Klaus

 

[LvW]

rishab, the slew rate is an indication of the opamp´s ability to follow a positive (or negative) step. Do you expect any influence of the time the input stays at the final level ?
Hence, you can use any repetition rate of the step function (squarewave) - as long as the width of the step function is sufficient to allow the output to reach the final value.