Class D
Class-D amplification is based on Pulse Width Modulation (PWM): a comparator converts the audio signal into high-frequency pulses, MOSFET transistors rapidly switch between on and off, and a low-pass filter reconstructs the smooth audio waveform.
Although conceptually existing before the 1990s, Class-D amplification experienced a revolutionary advancement with Powersoft’s introduction in 1995. Powersoft’s technology leverages PWM for highly efficient power conversion: it significantly reduces heat generation, minimizes power consumption, and increases amplifier power density.
How does a Class-D amplifier work?
The block diagram of a Class-D amplifier shows six numbered stages, from the audio signal input to the output filters.
- Audio signal input — the analog audio signal, which then passes through the input filter.
- Input filter — the analog audio signal passes through a low-pass filter to eliminate high-frequency radio interference (RF). This stage ensures a clean signal free from interference.
- Triangular wave generator — block 03 of the diagram, with the master clock.
- Comparator (PWM) — the comparator converts the filtered audio signal into high-frequency pulses. The pulse width, or duty cycle, directly correlates with the audio amplitude, enabling precise amplitude representation.
- Amplifier (MOSFET switching) — Metal–Oxide–Semiconductor Field-Effect Transistors (MOSFETs) rapidly switch between on and off at high frequencies, dramatically reducing power loss thanks to their low on-resistance and fast switching characteristics.
- Output filters — a low-pass filter reconstructs the smooth audio waveform from the high-frequency pulses, removing switching noise and ensuring clear, high-quality audio.
Key facts
- Powersoft introduced its amplifiers with Class-D technology in 1995.
- The term “Class-D” was used for the first time in 1955.
- Pulse Width Modulation was invented in 1938 by Alec H. Reeves.
- Class-D amplifiers are indispensable for large-scale events and fixed audio installations, where efficiency and reliability are critical.
What are the advantages of Class-D amplification?
- High efficiency and reliability — generates minimal heat, significantly prolonging component lifespan.
- Compact design — smaller power supplies and cooling systems reduce size and weight, which is great both for touring and fixed install applications.
- Lower operational costs — reduced power usage and simpler cooling infrastructure translate to significant cost savings.
- Superior audio quality — advanced feedback loops maintain exceptional linearity and minimal distortion.
- Green solution — the longevity of the products and their inherent efficiency lead to lower carbon emissions.
Where is Class-D amplification used?
Class-D amplifiers are indispensable for large-scale events and fixed audio installations, where efficiency and reliability are critical. Their compact design, with smaller power supplies and cooling systems, reduces size and weight: an advantage both for touring and for fixed install applications.
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