Design Of Class AB Folded-Cascode Audio Power Amplifier

The thesis is about a class AB audio amplifier design with low THD and folded cascode structure. Firstly, according to the spec and the circuit structure, we decided to use the folded cascode structure and designed the component parameter. Then, we use HSpice to do the simulation. The results showed that the unity gain bandwidth of the single op-amp was 48.5MHz while the quiescent current was 1.3mA. at the condition of 8 ohm load, the peak output current can achieve 250mA. The dc gain of this op-amp was 102dB, the phase margin was 54 degree and the PSRR was 104dB. Then, I use two of this op-amp to connect together with the BTL structure. Using this method can eliminate the coupling capacitor, lower the output stage peak current, and raise the output swing and power. Finally, the optimization work is done by calculating the two most important paramters THD and PSRR . The results about the whole audio power amplifier showed that the THD were about 0.1%; the PSRR were 57.4 to 117dB either when the output power was 1w or when the frequency of input signal was 1kHz.