Single-Ended, 2-Channel GaN Class D Amplifier – Evaluation Board

April 28, 2020 by Paul Shepard

The EVAL_AUDAMP24 e-mode GaN HEMT-based evaluation board from Infineon Technologies is a 2-channel, 225W/ch (4Ω at ±43V) or 250 W/ch (8Ω at ±63V) half-bridge class D audio power amplifier for high-end Hi-Fi audio systems. This evaluation board demonstrates how to use the IGT40R070D1 E8220 CoolGaN™ gallium nitride transistor together with the MERUS™ IRS20957SPBF controller IC, implement protection circuits, and design an optimum PCB layout.

Potential applications include Hi-Fi amplifiers, AV receivers, Home theater systems, Powered speakers, Musical instrument amplifiers, and other premium audio designs.

The reference design provides all the required housekeeping power supplies for ease of use. The 2-channel design is scalable for power and the number of channels.

The EVAL_AUDAMP24 features a two-channels self-oscillating type pwm modulator for the lowest component count, highest performance and robust design. This topology represents an analog version of a second-order sigma-delta modulation, having a class D switching stage inside the loop.

The benefit of the sigma-delta modulation, in comparison to the carrier-signal based modulation, is that all the error in the audible frequency range is shifted to the inaudible upper-frequency range by nature of its operation. Also, sigma-delta modulation enables the designer to apply sufficient error correction.

Summary of Features

  • Output power:
    • 225W x 2 channels (1% THD+N, 4Ω at ±43V)
    • 250W x 2 channels (1% THD+N, 8Ω at ±63V)
  • Multiple protection features:
    • Overcurrent protection (OCP), high- and low-side e-mode GaN transistors
    • Overvoltage protection (OVP)
    • Undervoltage protection (UVP), high- and low-side e-mode GaN transistors
    • Overtemperature protection (OTP)
  • PWM modulator:
    • Self-oscillating half-bridge topology with optional clock synchronization


  • Clean switching performance
  • Narrow deadtime for better THD
  • Easy to use: compatible with the MERUS™ IRS20957SPBF class D controller
  • Outstanding audio quality
  • High reliability