Design of a Low-power ECG Detecting Circuit

Electrocardiogram (ECG) detecting function nowadays is of great popularity. Through the analysis of electrocardiogram requirements in current wearable devices, a circuit is designed to realize the ECG detecting function. The main part of circuit is based on classic three-op-amps circuit, which can increase input impedance. Then, driven-right-leg circuit and capacitor coupling with filter were added to solve the problem of mismatching and electrode offset. Meanwhile, T-level (more than 1012 ohm) resistors for increasing input resistor were designed through Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFET) to save valuable space. At last, op-amps were replaced by Operational Trans-conductance Amplifiers (OTA) to decrease the power consumption. With the simulation of Small Signal AC behavior, noise and power consumption, the detecting circuit basically meets the Electrocardiogram detecting requirements, including bandwidth, differential gain, and input-referred noise. This design provides a suitable solution for realizing the electrocardiogram detecting function in portable devices especially like smart watches.