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Design of an extremely low cutoff frequency highpass frontend for CMOS ISFET via direct tunnelling principle

  • Jing Liang
  • , Yanjin Lv*
  • , Yuanqi Hu*
  • *Corresponding author for this work
  • Beihang University

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

Abstract

In this paper, the principle of direct tunnelling current is applied to eliminate the trapped charge in the passivation layer of CMOS ISFETs. A two-transistors frontend is implemented to achieve the most compact structure. For each ISFET the gate voltage will stabilise to a self-settled point regardless of its initial voltage (trapped charge) after reaching a balance between two tunnelling currents, from gate to source and from gate to drain. We have demonstrated the effects of different transistor sizes to this charge cancellation process. And based on above mentioned frontend, by adopting a feedback circuit to control the magnitude of the gate tunnelling current, the velocity of the cancellation process can be controlled. Test results show that the total duration of the process can be manipulated in 2 orders of magnitude. In addition to that, this design essentially performs a high-pass filter with cutoff frequency tunable from 14mHz to 0.3Hz approximately.

Original languageEnglish
Title of host publication2020 IEEE International Symposium on Circuits and Systems, ISCAS 2020 - Proceedings
PublisherInstitute of Electrical and Electronics Engineers Inc.
ISBN (Electronic)9781728133201
StatePublished - 2020
Event52nd IEEE International Symposium on Circuits and Systems, ISCAS 2020 - Virtual, Online
Duration: 10 Oct 202021 Oct 2020

Publication series

NameProceedings - IEEE International Symposium on Circuits and Systems
Volume2020-October
ISSN (Print)0271-4310

Conference

Conference52nd IEEE International Symposium on Circuits and Systems, ISCAS 2020
CityVirtual, Online
Period10/10/2021/10/20

Keywords

  • Direct tunnelling
  • Highpass filter
  • ISFET
  • Trapped charge

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