ISFET read-out circuit design for bio/chemical sensor applications

• Main Author: Sam, Jing Qing
• Other Authors: Yeo Kiat Seng
• Format: Final Year Project
• Language: English
• Published: 2014
• Subjects: DRNTU::Engineering::Electrical and electronic engineering::Integrated circuits
• Online Access: http://hdl.handle.net/10356/60881
• Institution: Nanyang Technological University

Recent demand in applications of biomedical-engineering has kept the fast pace for technological development and research in the sector. The invention of ISFET (Ion- Sensitive Field Effect Transistor) is one of the few devices that contributed to the biomedical engineering sector. From sensing of pH solutions to specific enzyme detection, the ISFET has proven its potential for many applications. To aid in the sensing capabilities of the ISFET, ISFET readout circuits were created and proposed by researchers. The performance in terms of sensitivity and power consumption of the pH sensing ISFET readout circuits were analysed. The ISFET readout circuits introduced in the final year project consist of the utilization of operational amplifier, which requires continuous power consumption to operate. Under certain readout circumstances, the continuous power consumption operational amplifier to monitor the pH changes might be seen as wastage. In this final year project, a switchable operational amplifier is proposed to replace the operational amplifier. Utilizing a clock pulse VPULSE to control the on and off frequency of switchable operational amplifier, the power consumption contributed by the switchable operational amplifier can be reduced significantly. The proposed switchable operational amplifier was simulated using 65nm design process kit provided by TSMC (Taiwan Semiconductor Manufacturing Company). A 1.2v VPULSE of duty cycle 50% was used, the power consumption contributed by the switchable operational amplifier was reduced by ~50% while achieving an average pH sensitivity of ~44.26mV/pH.