Research And Design Of Low Frequency Power Amplifier

The thesis require 20-30? circuit work environment, 5V supply voltage, 200-3400 Hz range of the operating frequency. Under this condition,design a low-frequency power amplifier which has strong practicability. The low-frequency power amplifier is composed of two circuits, which has same circuit structure and same device parameters. Single amplifier is a two-stage amplifier circuit, including a bias circuit, differential input,push-pull output and frequency compensation of four parts, the amplifier circuit don't amplify the voltage, achieve amplify the power only by amplifying the current. Bias circuit constitutes by the multiplexer current source, set up appropriate MOS transistor parameters,and provide the appropriate bias current for each node amplifier.Differential input part used cascode structure, tested to verify, the circuit can improve the signal quality, and optimize circuit performance. The push-pull output part uses two symmetrical push-pull output MOS transistor, the transient characteristics of the circuit simulation test, the results show that the circuit can output full waveform, effectively avoid the cross-over distortion of the waveform To prevent self-excited, the push-pull output section added RC frequency compensation structure. After the circuit configuration of the single amplifier circuit design is complete,the two identical amplifying circuit linked by way of bridge-connected, constitute the overall structure of the low-frequency power amplifier. Using bridge-connected can increase the maximum output power.After the basic structure of the circuit design is complete, using the M3524 0.5?m process model library, and use cadence software simulate the circuit's open-loop characteristics, the closed loop characteristics, maximum output power, SNR, PSRR,CMRR and other performance parameters, vrify the circuit whether meets the requirements.According to the simulation results, the single power amplifier's open-loop gain is 106.89 dB,voltage gain is zero, the phase margin is 83.731 dB, CMRR is 93.52 dB, SNR 94.69 dB, totalharmonic distortion is 0.353%, the simulation results is match to the design requirements.In conclusion, the power amplifier meet the performance expectations.