Biochemical sensor interface circuits with differential difference amplifier

A simple three-electrode CMOS interface system for electrochemical sensor is described. To maintain a constant potential between the reference electrode (RE) and working electrode (WE), only one differential difference amplifier (DDA) is exploited in this proposed design, while conventional sensor interface system requires at least 2 operational amplifiers and 2 resistors, or more than 3 operational amplifiers and 4 resistors for low voltage differential CMOS integrated interface circuits. The DDA with rail-to-rail design not only enables the full range operation to supply voltage but also provides simple interface system with small hardware and low power consumption. This new interface system was implemented in a 0.35um standard CMOS technology and experimentally verified.