Design Of Class AB Folded-Cascode CMOS Power Amplifier

Audio players such as popular CD, MP3 and DVD in the consumer electronic market have driven for low cost and high performance headphone power amplifiers. Majority of conventional power amplifiers are designed using bipolar technology on the basis of well-known merits of bipolar transistors. Although CMOS technology offers low cost alternative, they suffer major problems such as large size in output transistors, stability issues on driving low resistive in parallel with high capacitive load at high bandwidth, noise and so forth. Recently, with the fast development of CMOS technology, such problems have been solved in many aspects. In this paper, a class AB Cascode CMOS power operational amplifier with stable open-loop gain is presented. First,a proper selected Cascode amplifier structure is used in order to satisfy the design target, and then by using the method of power and current budget, appropriate device parameter is received. The simulated result shows that the unity gain-bandwith is 31 MHz, the quiescent supply current is 3.3mA and the output stage delivers maximum 50mA into a 32? load. The amplifier exhibits a 98.7dB open-loop gain at low frequency, phase margin is up to 108°, PSRR is 78dB and 3.11Vpp output at a 3.3V supply in a 0.5μm CMOS technology. On the other hand, in order to improve the input range of the amplifier, a complementary folded-Cascode operational amplifier is submitted. At last, a novel inner integrated circuit structure makes the outer coupling capacitance can be omitted. Thus make the system's volume even more economic.