用于ECG的低通带衰减OTA-C滤波器设计

Design of a Low Passband Attenuation OTA-C Filter Applied to ECG

以心电图(ECG)检测为应用背景,采用电流互抵技术和线性区晶体管偏置结构设计了一种超低跨导、高线性度的跨导运算放大器(OTA),其跨导达到了nA/V量级。在此基础上,根据信号传输函数搭建了一个4阶低通滤波器电路模型,其截止频率为250Hz,通带衰减为0.4dB,带内平均噪声为90.53μV(rms)·Hz-1/2,在ECG应用中拥有67dB的动态范围(THD≤1%)。使用Cadence Spectre软件进行仿真和调试,最后进行版图设计并流片。在不包括静电结构和压焊点的情况下,芯片版图面积为0.027mm2。电路供电电压为1.8V,具有很高的集成度,能应用于便携式ECG集成电路中。

Aiming at the applications of ECG detection, a very small transconductance and high linearity operational transconductance amplifier was designed based on current cancellation technique and triode biased transistors. The implementation of transconductance reached the level of nA/V. On this basis, a schematic model of 4th order low pass filter was built according to the signal transfer function. The cut-off frequency was 250 Hz with a low passband attenuation of --0.4 dB, the average noise in passband was 90.53 μV（rms） · Hz^-1/2 , and the dynamic range was 67 dB （THD≤1%） in the ECG applications. The circuit was simulated and debugged with the Cadence Spectre software followed by the layout. Finally, the layout was taped-out to test. Without ESD and PAD, the whole area of layout was 0. 027 mm^2. The supply voltage was 1.8 V. With such high integration, it can be used in the portable ECG IC.