An Optimized Controlled Current Source for Cancer Detection using Bioimpedance Spectroscopy

This work presents the design and validation of a Voltage Controlled Current Source (VCCS) aiming the Electrical Bio-Impedance Spectroscopy (EBS) application for Cervical Cancer Detection (CCD). Its topology relies on a modified variety of the classical Howland Current Source, whose schematic and layout were performed in the TSMC 65 nm CMOS process at a standard 1.2 V power supply. In this application, a stable sinusoidal load current must be provided with an amplitude of 10 μA to comply with international electromedical apparatus’ norms (IEC-60601-1) over a wide range of tissue impedance. Therefore, an advanced four-stage Operational Amplifier was customized to fulfill the VCCS’ requirements. The most noteworthy design outcomes were: a robust linearity, compatible with a subsequent 10-bit ADC sampling; a high output impedance, ranging from 1.59 GΩ at 100 Hz up to 159 kΩ at 1 MHz; an AC current amplitude consistently approaching 10 μA with a low DC offset of about ±1 μA for both 10 Ω and 5 kΩ loads at 1 MHz in Monte Carlo simulations; a compact area of 286x82 μm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> (without pads); a power dissipation close to 3.7 mW. Consequently, the obtained specifications position the proposed VCCS as an extremely prominent block suitable to be utilized for EBS/CCD.