A Bidirectional Front-end with Bandwidth Control for Actuation and Read-out of MEMS Resonating Sensors

L. Marchetti, Y. Berg, M. Azadmehr (Univ. College of Southeast Norway, Norway)

In this paper we propose a bidirectional front-end for resonating sensors with bandwidth control used to remove the high order oscillating modes. The electronic interface is based on an inverter working as amplifier biased by a voltage buffer, both realized in CMOS technology. The bandwidth of the amplifier can be tuned by varying a bias voltage which controls the high cut-off frequency of the front-end. A prototype was realized and tested with discrete components on a PCB. The tests were performed by using a RLC load which can be proved to be a good approximated model for a resonating sensor. The values for the load are R=100Ohm, L=10mH, C=270pF. Measurements were taken for Vdd=5V, Vdd=10V, Vdd=15V. Measurement results show that the bias voltage VHF affects both DC and AC characteristics of the amplifier, in particular the bandwidth varies in a range between a few kHz to a maximum of 5 MHz. A high order mode oscillation has been simulated by adding a sine wave generator at 2 MHz in series to the RLC load which was removed by filtering action of the amplifier.