Design Of Low Power Consumption High Slew Rate Operational Amplifier

Operational amplifier(op-amp) is one of the most important components in various electronic devices, especially in amplifier, filter, demodulation, sampling and impedance converter circuits. The parameters of op-amp have significant effects on the overall performance of electrical equipment.Slew rate and power consumption are the most important parameters of op-amps. Limited slew rate leads to signal distortion and low power consumption is today’s trend of circuits. In order to increase slew rate, higher supply current is needed. However, power consumption will increase in turn. Also, output signal will suffer from significant overshoot and oscillation. To make the whole circuit stable, larger compensation capacitor is needed. This results in lower slew rate. Therefore, low power consumption and high slew rate op-amp is the design bottleneck.This dissertation firstly proposes a two-stage op-amp based on Rohm 0.18μm technology. A control port is specially designed in order to make it easier to analyze the relationship between power consumption in term of bias current and response of operational amplifier. This chip sample is evaluated and the relationship among bias current, cutoff frequency, phase margin and direct current(DC) gain is analyze. These results provide theoretical evidence for a design of high slew rate, low power op-amp.Based on the analysis, this paper proposes a design of high speed, low power consumption operational amplifier, which is verified by HSPICE simulation. This work successfully decreases the value of Miller compensation capacitor more than three times, by using a new frequency compensation technology based on capacity multiplier. Also, a current control circuit is designed based on the difference between large signal response and small signal response. This design successfully increases slew rate by more than five times without influencing frequency compensation. It enhances the speed and quality of signal transforming.This op-amp has a power consumption of only 672 μW at typical supply voltage ±1.65 V. Slew rate is more than 94 V/μs. This design successfully realizes a high slew rate low power op-amp which has wide application prospect in high speed signal processing.