Low-voltage Micropower Rail-to-rail Output Cmos Operational Amplifier Design,

The paper designs a low voltage, micro power CMOS operational amplifier with rail-to-rail output. During the last years much effort has been put into the design of the analog CMOS low voltage micro power integrate circuits(IC). This is primarily due to the increasing consumption of batter powered electronics such as portable personal computers, cellular telephones, biomedical implants and so on. The low-voltage analog circuits, on the one hand, can obtain the low power. On the other hand, they can increase the stability of the circuits. One of the most important analog building blocks is the operational amplifier. Products of this kind of op-amp are available from many famous integrated circuits companies, such as the newest MCP604X series of Microchip Technology, Max406 series of Maxim. This paper has involved the following subjects: 1. All kinds of structure of low-voltage op-amp were compared and analyzed. Based on the investigation, the work presents a low voltage and micro power operational amplifier. 2. The paper studies the theoretics and synthesis of basic cells of a fold-cascode operational amplifier, such as differential pairs, cascode stages, low voltage wide-swing current mirrors, rail-to-rail output stages, miller compensation capacitors and so on. Some of MOSFETs are biased in weak inversion. 3. A push-pull output stage was used in the circuit to extend output voltage from rail to rail and A class AB biasing is used to improve the power efficiency of the circuit. 4. Under the Star-Hspice simulation, the DC gain is 119dB,and the current is about 1uA over the range of the supply.