A fully differential op-amp used in a high speed ADC is designed. This operational amplifier is consisted of a main OTA in folded cascade,four single-ended auxiliary OTA and a modified switched capacitor common mode feedback circuit. Gain-boosted technique has been introduced. Based on SMIC 0.18 μm,1.8 V process,Simulation has been run in Spectre under Cadence platform. The result shows that DC-gain of the amplifier is as high as 115 dB,unity-gain bandwidth is 805 MHz and the power consumption is 10. 5 mW. And it can reach an accuracy of 0.01% within 8 ns. This amplifier is specially used in a high speed pipelined ADC.%设计了一种用于高速ADC中的全差分运算放大器。该运算放大器由主运放、4个辅助运放和一种改进型开关电容共模反馈电路组成,主运放采用折叠式共源共栅结构,并引入增益增强技术提高增益。采用SMIC 0.18μm,1.8 V工艺,在Cadence电路设计平台中利用Spectre仿真,结果表明：运放增益达到115 dB,单位增益带宽805 MHz,而功耗仅为10.5 mW,运放在8 ns的时间内可以达到0.01%的建立精度,可用于高速高精度流水线( Pipelined) ADC中。
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