A Low-voltage Power Cmos Rail To Rail Op Amp Design

Operational amplifier is the most important unit circuit in the analog circuit. It is widely used in all kinds of analog and mixed-mode circuit. Recently, with the popularity of the portable electronic products and the decrease of the threshold voltage by the progress in the CMOS fabrication technology, low supply voltage, low power dissipation analog circuits become more and more popular. Therefore low supply voltage, low power dissipation circuit design techniques are also a hotspot in the research of analog circuit. With the ongoing reduction of the supply voltage and the dynamic range, the rail-to-rail input/output is necessary in the operational amplifier.Widespread investigation and study to the domestic and foreign technologies of the lower supply voltage, low power dissipation rail-to-rail input/output operational amplifier was done in this thesis. The thesis analyzes the work principles, merits and shortcomings of these technologies. Based on the absorption of these technologies, a low supply voltage, low power dissipation input/output rail-to-rail operational amplifier was designed. This operational amplifier is a two-stage operational amplifier. Supplementary differential input pare of transistors are used in the input stage. The folded-cascoded summing circuit is also used in the input stage to realize high gain. Current mirrors are used in the constant transconductance control circuit of the input stage. A supplementary class-AB structure output stage is used to enlarge output voltage range from rail to rail and improve power efficiency. A bandgap voltage source is designed to get bias voltage and current source circuits. Cascode current mirrors are used in the bias circuits to improve the PSRR. A common-gate compensation is used in the operational amplifier to remove the RHP zero.TSMC 0.35μm mixed-mode polycide and Star-Hspice 2004 are used to simulate the rail-to-rail operational amplifier. The simulated results show that the operational amplifier has a DC gain of 110dB, a GBW of 9.5MHz, a static power dissipation of 0.95mW, a phase margin of 73°,a voltage slew rate of 8.2V/μS, an input and output range of 0-3.3V, when operating at 3.3V power supply and a 20pF output load.