Class-D Audio Amplifier Using 1-Bit Fourth-Order Delta-Sigma Modulation

We present the design of a single-chip delta-sigma (DeltaSigma) modulation-based class-D amplifier for driving headphones in portable audio applications. The presented class-D amplifier generates output pulse signals using a single-bit fourth-order high-performance DeltaSigma modulator. To achieve a high signal-to-noise ratio and ensure system stability for a large input range, the locations of the modulator loop filter poles and zeros are optimized and thoroughly simulated. The test chip is fabricated using a standard 0.18-mum CMOS process. The active area of the chip is 1.6 mm². It operates for the signal bandwidth from 20 Hz to 20 kHz. The measured total harmonic distortion plus noise at the 32-Omega load terminal is 0.022% from a single 3-V power supply.