设计和研究了一种高增益恒跨导Rail-Rail CMOS运算放大器,输入级采用工作在亚阈值区的互补差分形式输入结构.与以往输入结构相比,不仅使输入共模电压达到Rail-Rail,而且降低了工作电压,提高了电源利用率.利用电流开关的作用使输入跨导在输入共模范围内恒定.中间级为MOS差分结构,并且同向驱动输出级使其具有推挽特性.采用嵌套米勒频率补偿使运算放大器稳定.整个电路采用华虹0.35 μmCMOS工艺参数进行设计,工作电压为3.0 V.利用OrCAD HSPICE仿真结果显示,在10 kΩ电阻和5 pF电容的负载下,运算放大的直流开环增益为110 dB,相位裕度为70°,单位增益带宽为45 MHz.%A high-gain constant transconductance rail-rail CMOS operational amplifier was designed. Input stage was complementary differential input structure and worked in the subthreshold region: reducing the supply voltage, improving power efficiency, making the input common voltage to Rail-Rail. Using the current switch in the input stage to keep transconductance constant during input common mode range. The second stage was MOS differential structure, which drives the push-pull output structure. By SHHIC 0.35 μm CMOS the circuit parameters design, operating voltage was 3.0 V. Using OrCAD HSPICE simulation results show that in the 10 kΩ resistor and 5 pF load capacitance, the op amp DC open loop gain of 110 dB, phase margin of 70 degrees, the unit gain bandwidth of 45 MHz.
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