提出了一种新的利用开关电容技术调节偏置电流值大小的电路,应用该电路可以精确调节跨导运放Gm值的大小。采用既具有电压共模负反馈(CMFB)电路,又同时具有工作在线性区的MOS管作源极反馈有源电阻,实现其良好线性度的跨导运放。设计了三阶椭圆函数低通滤波器,并实现其频率的精确可调。应用台积电(TSMC)2层多晶硅,4层金属(2P4M),3.3V电源电压,0.35μm CMOS工艺Spice model仿真得到的频响曲线与理想情况十分接近。
This paper presents a new circuit to tune Gm value of transconductor accurately which employs switched-capacitor technique to change the bias current of transconductor. A third order elliptical function lowpass filter with accurate tunable frequency is designed using transconductor that is not only with voltage common-mode negative feedback, but also with varying bias-triode transistors to improve the linearity of this circuit. Simulated results show that the practical frequency response of the filter is very near to that of idealized circumstance by applying TSMC 2-poly 4-metal 3.3V power supply 0.35 μm CMOS technology Spice model.