title: A Charge-Based Low-Power High-SNR Capacitive Sensing Interface Circuit.
abstract: This paper describes a low-power approach to capacitive sensing that achieves a high signal-to-noise ratio. The circuit is composed of a capacitive feedback charge amplifier and a charge adaptation circuit. Without the adaptation circuit, the charge amplifier only consumes 1 μW to achieve the audio band SNR of 69.34dB. An adaptation scheme using Fowler-Nordheim tunneling and channel hot electron injection mechanisms to stabilize the DC output voltage is demonstrated. This scheme provides a very low frequency pole at 0.2Hz. The measured noise spectrums show that this slow-time scale adaptation does not degrade the circuit performance. The DC path can also be provided by a large feedback resistance without causing extra power consumption. A charge amplifier with a MOS-bipolar pseudo-resistor feedback scheme is interfaced with a capacitive micromachined ultrasonic transducer to demonstrate the feasibility of this approach for ultrasound applications.
authors.forename: Sheng-Yu
authors.initials: SY
authors.lastname: Peng
authors.forename: Muhammad S
authors.initials: MS
authors.lastname: Qureshi
authors.forename: Paul E
authors.initials: PE
authors.lastname: Hasler
authors.forename: Arindam
authors.initials: A
authors.lastname: Basu
authors.forename: F L
authors.initials: FL
authors.lastname: Degertekin