具有精确恒定跨导偏置电路的G_m-C滤波器

G_m-C Filter with an Accurate Constant-G_m Bias Circuit

改进了一种精确恒定跨导偏置电路,通过对电流和晶体管尺寸的设计使主电路跨导恒等于外接高精度电阻跨导,与传统结构相比具有更高的精度。将该偏置电路应用于无线传感网芯片中9阶Gm-C椭圆低通滤波器的设计,使该滤波器省去了片上调谐电路的设计,在降低功耗的同时提高了精度,节省了面积。设计基于SMIC 0.18μm 1.8 V 1P6M CMOS工艺,芯片面积仅为0.9 mm×0.22 mm,测试结果表明,该滤波器的截止频率与设计值相差在1%以内,输入噪声电压小于25 nV/Hz,消耗电流仅为0.9 mA,满足无线传感网节点芯片的要求。

An accurate constant-transconductance bias circuit was improved.The bias circuit has higher accuracy compared with traditional architecture by properly designing the current as well as the transistor size to keep the main circuit transconductance being the same as the external high accuracy resistor transconductance.It was applied to 9th order Gm-C elliptic low pass filter for wireless sensor chips and the design of on chip tuning circuit was leaved out,which reduces the power consumption,improves accuracy and saves area.The chip was implemented in SMIC 0.18 μm 1.8 V 1P6M CMOS technology and consumes an area of only 0.9 mm×0.22 mm.Measurement results show that the cutoff frequency has only a difference of 1% from that of the simulated value,the input-inferred voltage noise is less than 25 nV/Hz,and the current consumption is only 0.9 mA.All these results meet the requirements of wireless sensor chips.