Low-voltage Micro-power Cmos Operational Amplifier Research And Design

In the research of biology and space technology, integrated circuits must work in low voltage and low static current. It is very important to develop micro power dissipation IC in the electronic industry. The operational amplifier (OPAMP), as the basic component in analog system and mix-signal system, can greatly improve the performance of IC in system level.Based on the basic principle of OPAMP and the unique character of low-voltage micro-power OPAMP, the schematics of the input, output stage and bias circuits are introduced in this paper, and can be used as the necessary theoretical support for the future circuit design.Taking into consideration of the technological requirements of low-voltage micro-power OPAMP, a two-stage micro-power OPAMP with the bias circuit is designed. In addition, the low-voltage folded cascode input stage, Class-AB output stage, bias circuit, frequency compensation and noise characteristics are analyzed in detail. In order to get extremely low static current, the OPAMP is biased in sub-threshold region properly.In layout design, the cross-couple structure is adopted in the input stage to minimize the MOSFET mismatch due to process, and consequently to lower the offset voltage in the circuits. Taking into consideration of ESD, the guard ring is adopted to isolate resistors and capacitors, thus to eliminate the influence in the main circuit by them.Based on TSMC 0.35um technology model and Hspice simulator, thorough circuit simulation is carried out. As can be seen form the results, the power dissipation is 3.3uW in 3V power supply, DC gain is 108dB, static current can lower to 1.1uA, unit gain band is 800kHz and phase margin can reach 60° .