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This paper presents an integrated digital class D audio power amplifier output stage implemented in a 40 V, 0.35 mum HV-CMOS technology. The integrated output stage consists of a full H-bridge, gate drivers, bootstrap diodes and protection circuits. Its performance was found to be better than previously published output stages implemented in SOI based BCD processes, which are typically more complex and costly. Experimental results show that low distortion is achieved with high efficiency. In open loop configuration, the minimum Total Harmonic Distortion plus Noise (THD+N) was measured to be 0.016%. The output stage has a maximum efficiency of 88% and delivers up to 38 W into a 4Omega Bridge-Tied Load (BTL).