Suitable Slew Rate in Op Amp circuit design


#1

Slew rate is one of an Op Amp’s important parameters. It reflects the output voltage conversion rate of the Op amp. In other words, it shows how fast the Op amp can respond to a rapid change of input level.

The below waveform shows an Op amp output signal response,

  • slew rate equation

slew rate

In your circuit design, the minimum required slew rate can be calculated as follows:

  • S ≥ 2 x π x freq x Vp ,
    freq = Maximun Signal Frequency (Hz)
    Vp = Peak Output Voltage (V)

For example, to amplify a signal with 5V peak and 25kHz maximum frequency, at least 0.785V/μs slew rate is required from your op amplifier by the above equation.

At the same time, please be aware of suitable slew rate when design an op amp circuit. Higher slew rates are not always better:

  1. Higher slew rate makes for higher operating current. This means higher power consumption.
  2. Faster slew rate will make higher bandwith. It may waste bandwidth and increase the complexity of circuit design.
  3. Higher slew rate will generate more EMI