SNR improvement in amplitude modulated resonant MEMS sensors via thermal-piezoresistive internal amplification

Effect of thermal-piezoresistive internal amplification on signal to noise ratio (SNR) of amplitude modulated resonant MEMS sensors (e.g. vibratory gyroscopes and Lorentz force magnetometers) has been studied in this work showing the possibility to significantly improve the detection limit. It has been shown that as the thermal-piezoresistive amplification sets in, noise rms value increases with a slower rate than the boost in vibration amplitude and output signal level, therefore the SNR increases. In addition to higher sensitivity due to internal amplification in such devices, improvement in SNR reduces the minimum detectable signal in presence of limiting Brownian and thermal noises. Preliminary measurement results show that increasing the DC bias current, which leads to a 3X increase in vibration amplitude, improves the SNR by a factor of 4.5 (6.6 dB).