The Design Of An Audio Power Amplifier

Audio Power Amplifier is widely used in high performance audio systems, stereo phonographs, servo amplifiers and instrument systems. Nowadays, people emphasize high power and high efficiency as well as high fidelity feature of audio power amplifier. So it's worth to design an Audio Power Amplifier with the features of high power and high efficiency.In this paper, a 20 watt audio power amplifier has been developed, which has class-AB output stage, and with Miller compensation internal to guarantee the stability of close loop. The chip has internal current limit,thermal shutdown and over-voltage protection circuit. When it is delivering high output power to the load or driving nonlinear reactive loads, the degradation of the output transistor or catastrophic failure of the whole circuit may happen without those internal protection circuit . It's capable of delivering 20 watt of output to a 4 ? or 8 ? load at±25 V supplies. The design takes advantage of advanced circuit techniques and process technology to achieve extremely low distortion levels even at high output power. The chip also has the following features: open loop gain of 100dB, current capability of 4A, slew rate of 10V/μs and power bandwidth of 40 kHz.Design of each block is described in detail, layout consideration is also presented in brief and the simulation waves are given. At last , the improvement of chip features is proposed as the feature work.The 4μm High Voltage Bipolar process is used to fabricate this chip. We use Cadence Spectre to run simulation, and results of system simulation indicate that the performance of this circuit meets exactly with the design goals. Meanwhile, we use Cadence Virtuoso to edit layout, and the chip has been in fabrication now.