Op Amp Speed: Bandwidth vs Slew Rate

HARI T O1

Expert 1675 points

Dear Team,

I was learning about the difference between opamp slew rate and bandwidth.

Everywhere it says slew rate is a large signal parameter and BW is a small signal parameter.

I have few questions

1)what you mean by large/small here because large/small are relative terms.What is the reference for large and small.

2)When do we need to give priority for slew rate compared to Bandwidth and vice versa

Regards

HARI

over 5 years ago

0 Michael Steffes over 5 years ago

Guru 48395 points

Morning Hari,

These articles connect the two idea,

https://www.edn.com/what-is-op-amp-slew-rate-in-a-slew-enhanced-world-part-1/

www.edn.com/.../

0 Ron Michallick over 5 years ago

TI__Guru**** 174306 points

Hello Hari,

Small in simulation means zero amplitude. Large means most of the available range between the power rails.

Bandwidth must support application gain and frequency product with some margin to spare.

Slew rate without without slew boost is easy. To get most of the data sheet slew rate (~90%) expect a 100mV input virtual zero error. (that means the difference voltage between the inputs increases by 100mV). Therefore slew rate looks good at gains of 1 or -1 where the input signal far exceeds the voltage needed to fully switch the input stage completely. In other words, if gain is high and input amplitude is small, expect output slew rate far less than data sheet spec.

If there is slew boost, then the input voltage difference may need to be much greater than 100mV to get that data sheet slew rate.

0 HARI T O1 over 5 years ago in reply to Michael Steffes

Expert 1675 points

Hi Michael,

Thank you. I Will read the articles provided.

Regards

HARI

0 HARI T O1 over 5 years ago in reply to Ron Michallick

Expert 1675 points

Hi Ron,

Thank you.

Regards

Hari

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Op Amp Speed: Bandwidth vs Slew Rate