A CCII-BASED HIGH IMPEDANCE INPUT STAGE FOR BIOMEDICAL APPLICATIONS

Abstract

An integrated current mode high impedance input stage designed for Electrocardiography (ECG) systems (or low frequency general applications) is presented. This feature becomes necessary when a two-electrodes ECG apparatus is used (e.g., in fetal ECG or heart monitoring in extreme sports) and a good response of the system to common mode signals is required. The proposed input stage, based on a bootstrap topology that simultaneously increases the ECG electrodes input impedance (from 5 ÷ 50 kΩ to about 50 MΩ) and amplifies the applied signal, is implemented by using a configuration that employs only two second generation current conveyors for each electrode. Post-layout simulations have proved that the proposed system is quite not sensible to electrodes mismatch and battery discharge.