DC RESTORE SCHEME FOR CAPACITIVE SENSING AMPLIFIERS WITH OPTIMAL NOISE FILTERING
摘要:
A capacitive sensing charge amplifier, e.g., in a direct current (DC) feedback network, may incorporate a switching capacitor, including a first control switch and a second control switch, which receives a switching signal to charge and discharges the switching signal to a virtual ground of a sense amplifier. Noise incorporated into the output of the sense amplifier (e.g., a MEMS output signal) is filtered by a demodulation signal at a demodulator such that the period average noise at the demodulator output equals zero. The time varying nature of the switching capacitor resistance generally reshapes the system's post-demodulation noise to reduce its low frequency output noise.
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