An integrated multiple-sensor chemical transducer

The main goal of this work has been improving transducer accuracy. This is accomplished by replacing the single transistor of CHEMFETs with an on-chip voltage-follower amplifier, and by integrating eight of these circuits onto a multiple-sensor transducer, which realizes the following features: (1) Eight transducers and control circuitry are included on a 54 x 140 mil chip. (2) The voltage-output circuit allows sensing with the solution at ground potential, and provides high-speed, on-chip multiplexing, so that only seven connections are made to the instrumentation. (3) Matched input transistors provide inherent compensation for variations in temperature, and the symmetrical design of the circuit reduces sensitivity to light. (4) Internal feedback improves input and output impedances and transfer function stability by more than three orders of magnitude. (5) The chip provides all of the data needed to implement multi-dimensional signal processing algorithms for separating desired signals from those of interfering chemicals.