This thesis presents a 1W analog / switching mixed-mode audio amplifier (MMA) for mobile application. The analog amplifier shows a good linearity. The switching amplifier shows a good efficiency. For mobile application good efficiency is necessary to save a battery life. And good linearity is also necessary in audio amplifier. To achieve these characteristics analog / switching mixed-mode amplifier is presented.
For mobile application MMA is integrated using 0.35um CMOS process. On-chip power MOSFET is used for few external devices. It operates at single 3.3V power supply. The bandwidth of the analog amplifier is about 12MHz and the frequency response is flat to the 500 kHz. The -3dB frequency of the MMA is about 300 kHz at 1/8W output power. The full power bandwidth at 4 Ω bridge connection is about 32 kHz. Maximum phase delay of the output signal is below 1.5 ˚. Maximum output power is about 1W at 4 Ω bridge connection. At this output power maximum efficiency about 87% is obtained. It shows a 0.1% THD at 1 kHz, 1/8W and 4Ω load.
The reverse recovery current free gate control method is also presented in this thesis. This control method is suitable for audio amplifier integrated circuit. The reliability of the chip is dependent on the on-chip power MOSFET. The reverse recovery current due to the conduction of the anti-parallel body diode gives a current stress to the power MOSFET. Moreover short and large reverse recovery current can also induce an EMI problem. The reverse recovery current free gate control can reduce the revere recovery current by the turn-off of the anti-parallel body diode during the dead-time.