A Class-D output bridge with dynamic dead-time, small delay and reduced EMI

Power efficient Class-D audio amplifiers are very popular in mobile applications, despite the potential electromagnetic interference (EMI) caused by their output stage. Going to higher power levels, more effort has to be put into the reduction of EMI without sacrificing audio performance and efficiency. This work presents a Class-D output stage with an adaptive driver concept. The proposed driver monitors each output transition and dynamically adjusts dead-time and driver strength to reduce EMI while maintaining high audio fidelity. The presented concept is implemented in a 180nm CMOS technology and verified by measurement.