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. 2019 Jun 13;19(12):2680.
doi: 10.3390/s19122680.

A Sub-mW 18-MHz MEMS Oscillator Based on a 98-dB Ω Adjustable Bandwidth Transimpedance Amplifier and a Lamé-Mode Resonator

Anoir Bouchami  1 , Mohannad Y Elsayed  2 , Frederic Nabki  3
Affiliations

A Sub-mW 18-MHz MEMS Oscillator Based on a 98-dB Ω Adjustable Bandwidth Transimpedance Amplifier and a Lamé-Mode Resonator

Anoir Bouchami et al. Sensors (Basel). .

Abstract

This paper presents a microelectromechanical system (MEMS)-based oscillator based on a Lamé-mode capacitive micromachined resonator and a fully differential high-gain transimpedance amplifier (TIA). The proposed TIA is designed using TSMC 65 nm CMOS technology and consumes only 0.9 mA from a 1-V supply. The measured mid-band transimpedance gain is 98 dB Ω and the TIA features an adjustable bandwidth with a maximum bandwidth of 142 MHz for a parasitic capacitance C P of 4 pF. The measured input-referred current noise of the TIA at mid-band is below 15 pA/ Hz . The TIA is connected to a Lamé-mode resonator, and the oscillator performance in terms of phase noise and frequency stability is presented. The measured phase noise under vacuum is -120 dBc/Hz at a 1-kHz offset, while the phase noise floor reaches -127 dBc/Hz. The measured short-term stability of the MEMS-based oscillator is ±0.25 ppm.

Keywords: 1-dB compression point; Lamé-mode MEMS resonator; MEMS-based oscillator; electrostatic actuation; input-referred noise; phase noise; quality factor; transimpedance amplifier.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Simplified diagram of the (a) exploded and (b) assembled views of the Lamé-mode MEMS resonator with corner supports [1].
Figure 2
Figure 2
SEM micrograph of the Lamé-mode MEMS resonator with corner supports [1].
Figure 3
Figure 3
MEMS-based oscillator functional diagram.
Figure 4
Figure 4
Circuit schematic of: (a) the proposed fully differential TIA design, and (b) the AGC.
Figure 5
Figure 5
Simplified equivalent circuit of the RGC input stage used for noise analysis.
Figure 6
Figure 6
Test setup of the MEMS-based oscillator in open-loop (solid lines) and closed-loop (dashed lines) with micrographs of the TIA and resonator.
Figure 7
Figure 7
Normalized resonator transmission characteristic curves for various output input amplitude levels for (a) Vp = 100 V and (b) Vp = 200 V.
Figure 8
Figure 8
Measured TIA (a) gain and (b) bandwidth, for different values of VCTRL_A and VCTRL_BW.
Figure 9
Figure 9
Measured TIA input-referred current noise.
Figure 10
Figure 10
Measured TIA gain for different input power levels, outlining the 1-dB compression point.
Figure 11
Figure 11
Measured open-loop gain and phase shift of the oscillator loop under vacuum at a polarization voltage of 100 V.
Figure 12
Figure 12
Measured phase noise in vacuum for polarization voltages of 100 V and 200 V.
Figure 13
Figure 13
MEMS oscillator signal short time stability at a 17.93 MHz central frequency (averaged over a five-minute timespan) with a polarization voltage of 100 V.
See this image and copyright information in PMC

References

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