A high output impedance CMOS current driver for bioimpedance measurements

Abstract

Advances in bioimpedance measurement applications need current drivers with high output impedance in the frequencies ranging from DC to a number of MHz. In particular, it needs greater than 10 MΩ output impedance at low frequencies, e.g., 10 kHz. This paper presents an current driver based on operational transconductance amplifiers (OTAs) using a feedback loop to provide over 10 MΩ output impedance ranging from DC to 10 kHz and 1 MΩ at 1 MHz. In addition, a stable performance over a wide frequency range (<4 MHz) is simulated. The circuit has been designed in a 0.6-μm CMOS process using ±2.5 V power supplies. Simulated results are presented.