A Fifth-Order Butterworth OTA-C LPF With Multiple-Output Differential-Input OTA for ECG Applications

Abstract

This brief proposes a fifth-order Butterworth operational transconductance amplifier-C (OTA-C) low-pass filter (LPF) with multiple-output differential-input (MODI) OTA structure and metal-insulator-metal capacitors for electrocardiography applications. The current division technology is used as an alternative output pair to provide multiple outputs and achieve high linearity. This technique reduces the number of OTAs of the fifth-order LPF from 11 to 6 as compared with the conventional structure. The design issue of linearity is also considered in the implementation of MODI OTA. The proposed filter is fabricated in a 0.18 μm complementary metal-oxide- semiconductor technology with an area of 0.12 mm2. The LPF achieved a total harmonic distortion of 49.8 dBc under a bandwidth of 50 Hz and input voltage of 86 mV <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">pp</sub> at a 1-V supply voltage. The total power dissipation is 350 nW.