Design considerations for an isfet multiplexer and amplifier

Design considerations for the multiplexing of pH-sensitive ISFETs are studied and discussed. Experimental results with an ordinary multiplex circuit show transients of the order of several seconds if the output voltage of the applied amplifier is required within an accuracy of 0.5 mV (corresponding to 0.01 pH unit). These transients appear to result from thermal instability of the ISFETs during switching operations, and can be cancelled by guaranteeing a constant chip dissipation. This necessitates the design of a special multiplexer circuit for multiplexing separate ISFETs. The output voltage of the applied amplifier then appears to be stable within 1 millisecond with the required accuracy

Sensors for biomedical applications

This paper considers the impact during the last decade of modern IC technology, microelectronics, thin- and thick-film technology, fibre optic technology, etc. on the development of sensors for biomedical applications

Prediction of the dynamic response of the potentiometric carbon dioxide electrode

The dynamic behaviour of the potentiometric carbon dioxide electrode is predicted by means of a digital simulation that considers both diffusion and reaction kinetics. The method allows for complete description of the electrode response without requiring the assumption that one of these processes can be neglected. The validity of the simulation was tested experimentally by using a commercial pCO2 electrode provided with various silicone rubber and teflon membranes. The measured values are in good agreement with those of the simulation

A polymer condenser microphone on silicon with on-chip cmos amplifier

In this paper the development of a capacitive microphone with integrated preamplifier is described. The condenser microphone is made by micromachining of polyimide on silicon, and is compatible with CMOS technology. Therefore, the structure can be realised by post processing on substrates containing integrated circuits, independently of the IC process. Microphones with a required DC bias voltage of 4 V have been realised on a CMOS substrate containing PMOS buffer preamplifiers. From the measurements on these structures, it is illustrated how an immediate improvement of 4.8 dB of the microphone sensitivity and noise level can be obtained by using the integrated preamplifier. The measured sensitivity of the integrated condenser microphone was 2.5 mV/Pa and the equivalent noise level (ENL) was 29.5 dB(A) SP

A bi-directional electrochemically driven micro liquid dosing system with integrated sensor/actuator electrodes

In this contribution a micro liquid dosing system is presented, which allows bi-directional manipulation of fluids (i.e. pushing out and pulling in of liquids) by the electrochemical generation and removal of gas bubbles. Bi-directionality is obtained by reversal of the actuation current thereby causing the earlier produced gasses to react back to water. This reduction of gas volume actively pulls liquid back into the system. The electrochemical actuator electrodes have been specially designed to perform the simultaneous measurement of conductivity, via which the total amount of gas can be estimated. As this amount equals the total dosed volume of liquid, dispensed volumes can be determined on-line during experiment

High-performance condenser microphone with fully integrated CMOS amplifier and DC-DC voltage converter

The development of a capacitive microphone with an integrated detection circuit is described. The condenser microphone is made by micromachining of polyimide on silicon. Therefore, the structure can be realized by postprocessing on substrates containing integrated circuits (IC's), independently of the IC process, integrated microphones with excellent performances have been realized on a CMOS substrate containing dc-dc voltage converters and preamplifiers. The measured sensitivity of the integrated condenser microphone was 10 mV/Pa, and the equivalent noise level (ENL) was 27 dB(A) re. 20 ¿Pa for a power supply voltage of 1.9 V, which was measured with no bias voltage applied to the microphone. Furthermore, a back chamber of infinite volume was used in all reported measurements and simulation

On the integration of a microdialysis-based microTAS with calibration facility on a silicon-glass sandwich

The integration is discussed of all parts of a microdialysis-based micro Total Analysis System or ¿TAS. In particular a microdialysis probe, a potentiometric and amperometric ion- and enzyme sensor and a calibration dosing pump have been developed separately using different precision machining techniques. By modifying and adapting these parts they can be realized in one generic technology consisting of a stack of a silicon and a glass wafer. The silicon wafer contains the double lumen microdialysis probe connections, a dosing pump chamber with meander formed cavities containing the calibration solutions and small cavities for both the potentiometric and amperometric sensor. The glass wafer contains all the electrical contacts and wires for the sensors, the pump and Interconnections. Both wafers are anodically bonded to each other, yielding a hermetically sealed liquid handling syste