Bridge Resistance Deviation-to-Period Converter for Resistive Biosensors

Abstract

A bridge resistance deviation-to-period (BRD-to-P) converter is presented for interfacing resistive biosensors. It consists of a linear operational transconductance amplifier (OTA) and a current-controlled oscillator (CCO) formed by a current-tunable Schmitt trigger and an integrator. The free running period of the converter is 1.824 ms when the bridge offset resistance is 1 kΩ. The conversion sensitivity of the converter amounts to 3.814 ms/Ω over the resistance deviation range of 0-1.2 Ω. The linearity error of the conversion characteristic is less than ±0.004 %.