A 0.25W fully integrated class-D audio power amplifier in 0.35μm CMOS

A fully integrated class-D audio power amplifier using Pulse Width Modulation (PWM) technique is presented. The output stage is an H-bridge with 5.75 mm wide nMOS transistors and 15 mm wide pMOS transistors, which can deliver up to 0.25 Wrms to an 16 Ω load. The chip measuring 1.2×2.4 mm², including pads, was fabricated in a 0.35 μm CMOS process. It uses a single 3.3 V supply and a PWM carrier frequency of 2.5 MHz. The chip was designed and simulated with Cadence IC design tools as a student project in the course IC-project and verification at Lund University. The chip was verified and works well with a measured THD+N of 0.5% and efficiency of 76% at 0.25 Wrms output power into 16 Ω.