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Opamp Bandwidth or Slew rate-Opamp Speed

Hari T O0
Genius 3820 points

Dear Team,

May I know is there any relation between Op-amp Bandwidth and slew rate?

For determining the opamp speed Do I need to consider Bandwidth or Slew rate.

When I did a google search I found that for "small" signals we need to consider BW, and for "Large" signals need to consider slew rate-Please correct if it is wrong.But

they are not telling small/Large w.r.t what because "small" and "Large" are relative terms.

Regards

Hari

  • 0
    TI__Guru 52446 points

    HI Hari,

    When discussing the settling time response of the amplifier, you have to consider both the bandwidth and slew rate of the amplifier.

    -Bandwidth is a small-signal parameter (small-signal steps such as less than ~100mV at the input of the amplifier) that determines the frequency response of the amplifier.

    -Slew rate is a large signal parameter (large-signal step such as a 1V step at the input of the amplifier) defined as the maximum rate of change of an op amp’s output voltage and is given units of volts per microsecond.  

    Please note, the way in which an amplifier operates is not always fully large-signal or small-signal. In fact, there’s a gradual transition between these two operating conditions.   The transition from small-signal to large-signal depends on the amplifier’s design and technology.  CMOS amplifiers tend to reach slew limit for signals greater than 100mV, and bipolar amplifiers can slew limit at even lower input voltages.  

    Please refer to the following sections of TI precision Labs videos that discuss slew rate and bandwidth in great detail.  The two video sections at the bottom take a look at the difference between large signal and small signal behavior and at the transition from small signal to large signal response, as well as the effects of gain on op amp behavior.

    Thanks and Regards,

    Luis

    TI Precision Labs - Op Amps: Bandwidth

    TI Precision Labs - Op Amps: Slew Rate

    TI Precision Labs - Op Amps: Slew Rate 2

    TI Precision Labs - Op Amps: Slew Rate 3