A novel parametric-effect MEMS amplifier

This paper presents the theory and measurements of a mechanical parametric- effect amplifier with a 200-kHz input signal and a 1.84-MHz output signal. The device used is a MEMS time-varying capacitor which is composed of an ar ray of low-stress metallized silicon-nitride diaphragms, and is pumped by a large-signal voltage at 1.64 MHz. This induces a large change in the capac itance, and results in parametric amplification of an input signal at 200 k Hz. The parametric amplifier capacitance is 500 pF, resulting in an output impedance of 140 Omega. A higher impedance can also be achieved with a lowe r capacitance. To our knowledge, this device is the first-ever MEMS mechani cal up-converter parametric-effect amplifier developed with an up-conversio n ratio of 9 : 1. The measurements agree very well with theory, including t he effect the series resistance and the Q of the MEMS time-varying capacito r. The application areas are in amplifiers which operate at very high tempe ratures (200 degreesC-600 degreesC), under high particle bombardment (nucle ar applications), in non-semiconductor-based amplification, and in low-nois e systems, since parametric amplifiers do not suffer from thermal, shot, or 1/f noise problems.