A 570-kbps ASK demodulator without external capacitors for low-frequency wireless bio-implants

Chua Chin Wang, Tzung Je Lee, U. Fat Chio, Yu Tzu Hsiao, Jia Jin J. Chen

Research output: Contribution to journalArticlepeer-review

13 Citations (Scopus)


This paper proposes a novel structure of ASK (amplitude shift keying) demodulators, which requires no external capacitors, for implantable micro-stimulators. By using a traditional β multiplier reference to detect the signal envelope, followed by a Schmitt trigger and a load driver, the large off-chip capacitor in traditional ASK demodulators is not required any more. Therefore, the proposed circuit possesses small area to be integrated in an SOC (system-on-chip). Besides, due to the lack of the large capacitor, the proposed circuit can operate with a higher data rate using lower frequency carriers. The proposed circuit is integrated in an implantable micro-stimulator on silicon using 0.35 μ m 2P4M CMOS process. The area of the proposed circuit occupies merely 0.039 mm2 with a maximum power dissipation of less than 12 mW (including the power consumption of the analog circuits of the micro-stimulator) by measurement results on silicon. Moreover, the measurement results verify that the proposed ASK demodulator can detect the ASK modulated signal up to 570 kbps data rate at 2 MHz carrier frequency when the modulation index is 10%.

Original languageEnglish
Pages (from-to)130-136
Number of pages7
JournalMicroelectronics Journal
Issue number1
Publication statusPublished - 2008 Jan

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Atomic and Molecular Physics, and Optics
  • Condensed Matter Physics
  • Surfaces, Coatings and Films
  • Electrical and Electronic Engineering


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