Yoshiki Takezawa

Wide-range and precise tissue impedance analysis circuit with ultralow current source using gate-induced drain-leakage current

This paper presents a bioelectrical impedance analysis circuit with ultralow-current source using gate-induced drain-leakage (GIDL) current for biomedical applications. The proposed circuit consists of an ultralow-current reference circuit, a minimal voltage measurement block, a precise current source block, and a digital control logic circuit. The reference circuit generates pico-ampere-order currents based on GIDL current of an n-channel MOSFET. Fabricated in a 0.18μm 1P6M standard CMOS technology, the impedance analysis circuit occupies 0.27mm2 and can measure impedance range from 100Ω to 10MΩ. Experimental results shows that the fabricated current source using GIDL current generates a quite stable ultralow-current of 50pA, 100pA and 200pA, respectively. In addition, the proposed analysis circuit successfully measures the electrode-tissue interface impedance and tissue impedance by functional verification using monolayer and inhomogeneous agarose gel test setup phantom.