Op Amp Slew Rate Calculator

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Table of contents

• How to use
• Common mistakes
• Definitions
• Methodology
• Limitations & assumptions
• Sources

Slew rate: How fast an op amp output voltage can change, usually written in volts per microsecond (V/us). Data sheet slew rate is a large-signal output speed rating [2].

Peak voltage: The distance from the sine wave center line to its highest point.

Peak-to-peak voltage: The full top-to-bottom height of the wave. For a sine wave, peak voltage is half of peak-to-peak voltage.

RMS voltage: The effective sine-wave voltage often used in audio and AC measurements. For a sine wave, peak voltage equals RMS voltage times sqrt(2).

Extra safety margin: A percent added above the math-only minimum so the chosen op amp is not right at the limit.

Gain bandwidth product: A rough small-signal speed rating. In this calculator, the minimum check is signal frequency times noise gain.

Noise gain: The gain used for the bandwidth check. For many non-inverting circuits, it is the closed-loop gain.

Slew-rate headroom: How far the entered op amp slew rate is above or below the recommended slew rate. Positive is extra room. Negative is a shortage.

Mistake: Entering an input signal in Output voltage (V) when the op amp has gain.
Fix: Use the expected output swing at the op amp output for Output voltage (V).

Mistake: Leaving What does the voltage number mean? on Peak voltage when the oscilloscope reading is peak-to-peak.
Fix: Change What does the voltage number mean? to Peak-to-peak voltage for a top-to-bottom scope reading.

Mistake: Using RMS mode in What does the voltage number mean? for a square wave, triangle wave, or pulse.
Fix: Use RMS voltage for a sine wave only, or convert the waveform to the peak value before using Output voltage (V).

Mistake: Treating Op amp slew rate (V/us) as if it guarantees a clean signal at every load and output level.
Fix: Add Extra safety margin (percent) and check the data sheet conditions near your supply voltage, load, and output swing.

Mistake: Reading a negative Slew-rate headroom as zero margin.
Fix: A negative Slew-rate headroom means the op amp is short; lower the frequency, lower the output swing, or choose a faster op amp.

Mistake: Passing Op amp check but ignoring Bandwidth check.
Fix: If Op amp gain bandwidth product (MHz, optional) is known, enter it with Noise gain for bandwidth check (V/V) to catch a small-signal speed limit.

• The formulas are for sine waves. RMS conversion in What does the voltage number mean? assumes a sine wave, not a square, triangle, pulse, or clipped signal.
• Slew rate is a large-signal limit. Real op amps can distort before the exact math limit, especially near output swing limits, with heavy loads, or with supply voltages different from the data sheet test.
• The gain bandwidth check is a rough small-signal check. It does not replace data sheet gain and phase plots, output swing curves, or stability checks.
• Output voltage must be the op amp output swing. If your circuit has gain, do not enter the input signal unless the gain is 1.
• Extra safety margin (percent) increases the recommended slew rate and lowers the calculated maximum frequency or maximum output voltage.
• The calculator does not check output current, capacitive-load stability, input common-mode range, power dissipation, or supply rail limits.

How the calculator turns voltage into peak voltage

The slew-rate formula uses peak output voltage, so the entered voltage is first converted to a sine-wave peak value.

Vpeak = Ventered for peak voltage

Vpeak = Vpp / 2 for peak-to-peak voltage

Vpeak = Vrms * sqrt(2) for RMS sine-wave voltage

Sine-wave slew rate

For a sine wave, the fastest slope happens at the center crossing. The standard minimum slew-rate relationship is based on the maximum slope of Vout = Vpeak * sin(2 * π * f * t).

SR_min_V_per_us = 2 * π * f_hz * Vpeak * 0.000001

The 0.000001 factor converts volts per second to volts per microsecond. If the op amp cannot change fast enough, a sine wave can start to look triangle-like [1].

Margin and op amp check

Extra safety margin raises the target above the math-only minimum.

SR_recommended = SR_min_V_per_us * (1 + margin_percent / 100)

When checking a data sheet value, the calculator compares the entered Op amp slew rate (V/us) with the recommended value and keeps signed headroom.

headroom_percent = (SR_available / SR_recommended - 1) * 100

A positive headroom means the data sheet slew rate is above the recommendation. A negative headroom means it is below the recommendation.

Solving backward

For highest sine-wave frequency, the calculator rearranges the same formula and includes the safety margin.

f_max_hz = (SR_available * 1000000) / (2 * π * Vpeak * (1 + margin_percent / 100))

For highest output voltage, it solves for peak voltage first, then also reports peak-to-peak and RMS sine-wave values.

Vpeak_max = (SR_available * 1000000) / (2 * π * f_hz * (1 + margin_percent / 100))

Vpp_max = 2 * Vpeak_max

Vrms_max = Vpeak_max / sqrt(2)

Bandwidth check

If Op amp gain bandwidth product (MHz, optional) is entered, the calculator also computes a rough minimum gain bandwidth product.

required_GBW_MHz = (f_hz * noise_gain) / 1000000

Bandwidth check passes when the entered gain bandwidth product is at least this value.

Mini-example

For a 20,000 Hz sine wave with 5 V peak output and 0 percent margin, the minimum slew rate is:

SR_min = 2 * π * 20000 * 5 * 0.000001 = 0.6283185 V/us

So a part rated at 1 V/us has about (1 / 0.6283185 - 1) * 100 = 59.2 percent slew-rate headroom before any added margin.