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设计了一种全集成频率可调的OTA-C滤波器,主要应用于低频率生理信号的处理。其中,跨导放大器(OTA)采用串并联金属氧化物半导体场效应晶体管(MOSFET)阵列结构。通过改变外部控制电压,进而改变OTA的跨导值,可以实现滤波器截止频率可调。滤波器采用标准的0.18μm CMOS工艺,电源电压为1.8 V。当OTA的偏置电流为0.01μA时,其等效跨导低至1.3×10~(-10)S,得到OTA-C滤波器的截止频率为0.2 Hz。调节外部电压,使偏置电流在0.01～0.5μA之间变化,OTA的等效跨导值为1.3×10~(-10)～1.2×10~(-9)S,OTA-C的截止频率为0.2～2 Hz。
A fully integrated frequency tunable OTA-C filter is designed, which is mainly applied to the processing of low frequency physiological signal. Among them, the transconductance amplifier (OTA) series and parallel-connected metal oxide semiconductor field effect transistor (MOSFET) array structure. By changing the external control voltage and then changing the transconductance value of the OTA, the filter cut-off frequency can be adjusted. The filter uses a standard 0.18μm CMOS process with a supply voltage of 1.8V. When the bias current of OTA is 0.01μA, the equivalent transconductance is as low as 1.3 × 10 ~ (-10) S, and the cut-off frequency of OTA-C filter is 0.2 Hz. Adjust the external voltage, the bias current varies between 0.01 ~ 0.5μA, the equivalent transconductance of OTA is 1.3 × 10 ~ (-10) ~ 1.2 × 10 ~ (-9) S, OTA-C cut-off frequency Is 0.2 ~ 2 Hz.