Search results for "ISFET"
showing 4 items of 4 documents
Transconductance Converters Based on Current Mirrors Applied to pH Measurement Using ISFET Sensors
2009
New transconductance circuits (V/I converters) are designed based on current mirrors and operational amplifiers. Their input/output characteristics and the influence of DC parameters are obtained. Experimental results were performed, comparing them with the simulated results. An electronic instrumentation circuit is designed based on one of the transconductance converters analyzed. The purpose of this circuit was to condition the response of an ion-sensitive field-effect transistor (ISFET) to measure pH. In the proposed application, the V/I converter presented provides the stability and accuracy of the ISFET operating point, making an easy characterization procedure and the design of multic…
ISFET drawbacks minimization using a novel electronic compensation
2004
Ion sensitive field effect transistor (ISFET) and membrane field effect transistor (MEMFET) have some drawbacks related to: long-term drift, hysteresis and thermal drift. These factors limit the accuracy of ISFET/MEMFET based measurements systems, specially for continuous or long period measurements. Due to its accuracy, repeatability and easy-to-use features, electronic instrumentation systems are the best tools to design ISFET/MEMFET based measurement systems. A well-designed hardware and a qualified virtual instrumentation software are the key factors to overcome and compensate hysteresis, thermal and long-term drifts ISFET/MEMFET limitations. The paper is dedicated to show an instrument…
Novel voltage-controlled conditioning circuit applied to the ISFETs temporary drift and thermal dependency
2003
This paper describes a novel conditioning circuit applied to ion-sensitive field-effect transistors/membrane-ion-sensitive field-effect transistors (ISFETs/MEMFETs) sensors. The novel conditioning circuit allows the sensor polarization with the needed either voltage or current required in each application, thanks to two completely independent voltage-controlled blocks (current and voltage blocks). The control of the voltage block is the most critical point in our design because the voltage block maintains the sensor feedback stable, avoiding the thermal and temporary drifts of the sensor feedback.
Novel constant current driver for ISFET/MEMFETs characterization
2001
Abstract In the present work a new constant current driver for ISFETs and MEMFETs sensors has been developed. The proposed circuit maintains the ISFET/MEMFET operation point at constant drain–source current and voltage. The combination of some programmable current sources and an appropriate selection of a simple precision resistor allow a good ISFET/MEMFET polarization. The use of operational amplifiers with low offset and drift are required to provide the buffering function needed by the sensor.