Simple Explanation

The speed at which an amplifier can change its output in response to an input signal.

Concise Technical Definition

Slew rate refers to the maximum rate at which an amplifier's output voltage can change in response to its input voltage, typically measured in volts per millisecond (V/ms). A higher slew rate indicates that the amplifier can more accurately follow rapid changes in the input signal, which is essential for reproducing subtle dynamics and fast transients in audio. To measure slew rate, a large amplitude step function is applied to the amplifier, and the slope of the output waveform is observed. The rate of change is determined by how quickly the amplifier can charge and discharge its internal compensation capacitor.

Layman-Friendly Analogy

Imagine trying to follow a fast-moving object with your eyes—if you can keep up with it quickly, your "slew rate" is high. If you can’t keep up, you’ll miss parts of the movement. In audio, an amplifier’s slew rate determines how quickly it can follow fast, sharp changes in sound, like a sudden cymbal crash or the attack of a snare drum.

Industry Usage Summary

Slew rate is an important specification for amplifiers, especially in high-fidelity audio systems, where precise reproduction of dynamic and transient signals is crucial. A higher slew rate allows the amplifier to reproduce fast changes in sound without distortion, ensuring that the audio remains clear and accurate. It is particularly relevant for amplifiers used in professional audio systems, where subtle nuances in music and speech must be captured faithfully. Amplifiers with low slew rates may have trouble keeping up with rapid sound changes, leading to distortion or smearing of the audio.

Engineering Shortcut

The maximum rate at which an amplifier can change its output voltage in response to its input, measured in V/ms.

Full Technical Explanation

Slew rate is the maximum rate of change in the output voltage of an amplifier in response to its input signal. It is an important parameter for evaluating an amplifier's ability to reproduce high-frequency transients and fast audio events. Slew rate is typically measured in volts per millisecond (V/ms) and is determined by applying a large amplitude step function to the amplifier, then observing the slope of the output waveform on an oscilloscope. In a "perfect" amplifier, the output would rise vertically in response to a step input, but in reality, the amplifier exhibits a slope due to its finite current capabilities, which govern how quickly it can charge and discharge the internal compensation capacitors. A higher slew rate allows for better reproduction of high-frequency content and fast, dynamic events in the audio signal, making it a key factor for high-performance amplifiers in both consumer and professional audio systems.