资 源 简 介
跨导运算放大器是模拟电路中的重要模块，其性能往往会决定整个系统的效果。这里设计了一种适用于高阶单环Sigma-Delta调制器的全差分折叠式共源共栅跨导运算放大器。该跨导运算放大器采用经典的折叠式共源共栅结构，带有一个开关电容共模反馈电路。运算放大器使用SIMC 0.18 μm CMOS混合信号工艺设计，使用Spectre对电路进行整体仿真，仿真结果表明，负载电容为5 pF时，该电路直流增益可达72 dB、单位增益带宽91.25 MHz、相位裕度83.35°、压摆率35.1 V/μs、功耗仅为1.41 mW。本设计采用1.8 V低电源电压供电，通过对电路参数的优化设计，使得电路在低电压条件下仍取得良好的性能，能满足Sigma Delta调制器高精度的要求。
Abstract:
Operational Transconductance Amplifier is an important module in the analog circuit， which always determines the performance of the whole system. A low-voltage fully-differential folded-cascode OTA is designed for high-order Sigma Delta modulator in the paper. The OTA uses classic folded cascode structure. Auxiliary feedback amplifiers and the switched capacitor common mode feedback circuit are employed. The OTA is fabricated on SMIC 0.18μm CMOS mixed signal process. The simulation result of whole circuit in Spectre，shows that the open-loop DC gain is 72dB ， the unity-gain bandwidth is 91.25MHz， the phase margin is 83.35°， the slew rate is 35.1V/μs at a driving load of 5pF， and the total power consumption of the device is only 1.41mW. A low-voltage supply 1.8V is adopted in the design， and the parameters of circuit are optimized to achieve well performance in this low-voltage supply. This amplifier is suitable to the application for high resolution Sigma Delta modulator.
