Title :
An auto-offset-removal circuit for chemical sensing based on the PG-ISFET
Author :
Yan, Liu ; Georgiou, Pantelis ; Constandinou, Timothy G. ; Garner, David ; Toumazou, Chris
Author_Institution :
Dept. of Electr. & Electron. Eng., Imperial Coll. of Sci., Technol. & Med., London, UK
Abstract :
This paper presents a novel readout circuit for a pH sensitive programmable-gate ion-sensitive field effect transistor (PG-ISFET) to overcome bias issues due to threshold voltage variation and increase output-referred sensitivity. Compared to other commonly-used ISFET readouts, this circuit uses two extra programmable nodes which are driven by a feedback configuration. Using the device in a source follower configuration, one node is used to evaluate and cancel the offset of the intrinsic device while the other tracks and amplifies changes in pH. A sample and hold protocol has been developed to minimize the leakage effects and improve the pH sensing range. The system has been designed and fabricated in AMS 0.35 mum, to compensate for a threshold voltage variation of plusmn10.5 V and provide a pH sensitivity of 200 mV/pH.
Keywords :
CMOS integrated circuits; chemical sensors; ion sensitive field effect transistors; pH measurement; programmable circuits; CMOS ISFET sensor interface; PG-ISFET; autooffset-removal circuit; chemical sensing; pH sensitive programmable-gate ion-sensitive field effect transistor; sample and hold protocol; size 0.35 mum; source follower configuration; threshold voltage variation; voltage -10.5 V; voltage 10.5 V; Biomedical engineering; Biomedical measurements; Biomembranes; Chemical technology; Electrodes; FETs; MOSFET circuits; Protocols; Sensor phenomena and characterization; Threshold voltage;
Conference_Titel :
Circuits and Systems, 2009. ISCAS 2009. IEEE International Symposium on
Conference_Location :
Taipei
Print_ISBN :
978-1-4244-3827-3
Electronic_ISBN :
978-1-4244-3828-0
DOI :
10.1109/ISCAS.2009.5117968
