A 4.5 GΩ-Input Impedance Chopper Amplifier with Embedded DC-Servo and Ripple Reduction Loops for Impedance Boosting to Sub-Hz

Xuan Thanh Pham, Duc Nha Duong, Ngoc Tan Nguyen, Nguyen Van Truong, Jong Wook Lee

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)

Abstract

Achieving a high input impedance {Z} {in} is important for the instrumentation amplifier (IA) performing neural and biopotential signal sensing. Previously, impedance boosting techniques have been used with a positive feedback loop (PFL) driven by the output or auxiliary (AUX) path driven by the input. We propose that the conventional approach to DC-servo loop (DSL), which blocks the electrode offset (EOS), does not fully enable the function of a PFL or AUX path. This results in either limited impedance boosting or reduction of a low-frequency {Z} in in the sub-Hz band. To solve this problem and achieve {Z} in boosting down to sub-Hz, we propose a new approach to DSL for a capacitively-coupled chopper instrumentation amplifier (CCIA). The proposed DSL is realized using a 30-nA opamp, and the AUX path is designed using a 450-nA duty-cycled buffer. The CCIA achieves a gain of 40 dB and is implemented using a 0.18μ m CMOS process with an area of 0.19 mm2. The measured results show that {Z}in is increased by 184 times up to 4.6 GΩ at 0.01 Hz. Compared to the CCIA using conventional DSL, {Zin is improved by 7.8 times. An input-referred noise of 2.1μ Vrms is achieved at 2.14μ W.

Original languageEnglish
Article number9136768
Pages (from-to)116-120
Number of pages5
JournalIEEE Transactions on Circuits and Systems II: Express Briefs
Volume68
Issue number1
DOIs
Publication statusPublished - Jan 2021

Keywords

  • Instrumentation amplifier
  • chopping
  • dc servo loop
  • input impedance
  • input-referred noise
  • neural sensing

Fingerprint

Dive into the research topics of 'A 4.5 GΩ-Input Impedance Chopper Amplifier with Embedded DC-Servo and Ripple Reduction Loops for Impedance Boosting to Sub-Hz'. Together they form a unique fingerprint.

Cite this