Research And Analysis Of Amplifier Frequency Compensation

With the scaling down of device sizes and supply voltages, the design emphasis had shifted from the basic qualities towards the ability of circuits to operate at a low supply voltage, consuming a minimum amount of power, demanding on accuracy and noise at the same time. Single-stage amplifiers based on the cascading technique were no longer suitable for achieving high dc gains under low supply voltages. More circuit designers were aware of the importance of low-voltage multistage amplifiers. However, all multistage amplifiers suffered close-loop stability problems due to their multiple-pole nature. Therefore, many frequency compensation topologies had been proposed.Firstly, two-stage amplifier frequency compensation topology had been analy -zed in terms of theory in the paper detailedly, based on amplifier characteristic. C -onsidering the parameter of amplifier based compensation technology in general, two circuits had been designed for different compensation theory. We analyzed the circuit structure and the design process for each circuit. Expressions of DC gain, p -ole, and common mode input range were calculated. After that, based UMC 0.6 um 2P2M BICMOS MODEL, every parameter had been simulated and analyzed, including open gain, phase margin, common mode input range, differential mode input range, power supply rejection ratio, common mode rejection ratio. A comparison was given for the two circuits above. The two two-stage amplifiers had good performance index, high unity gain bandwidth, good frequency characteristic, and could be applied well in practice.Then, three-stage amplifier frequency compensation topology had been analyzed in terms of theory detailedly. Two circuits of three-stage amplifier had been designed for different compensation theory. We analyzed the circuit structure in general. Expressions of DC gain, pole were calculated. On the basis of UMC 0.6 um 2P2M BICMOS MODEL, every parameter had been simulated and analyzed for each three-stage amplifier proposed in the paper, including open gain, phase margin, common mode input range, differential mode input range, power supply rejection ratio, common mode rejection ratio. A comparison was given for the two three-stage amplifier circuits in the fourth chapter in the end..Finally, conclusions were given for circuits in the paper.