The resonant gate transistor

Abstract

A device is described which permits high- <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</tex> frequency selection to be incorporated into silicon integrated circuits. It is essentially an electrostatically excited tuning fork employing field-effect transistor "readout." The device, which is called the resonant gate transistor (RGT), can be batch-fabricated in a manner consistent with silicon technology. Experimental RGT's with gold vibrating beams operating in the frequency range 1 kHz < f <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</inf> < 100 kHz are described. As an example of size, a 5-kHz device is about 0.1 mm long (0.040 inch). Experimental units possessing <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</tex> 's as high as 500 and overall input-output voltage gain approaching + 10 dB have been constructed. The mechanical and electrical operation of the RGT is analyzed. Expressions are derived for both the beam and the detector characteristic voltage, the device center frequency, as well as the device gain and gain-stability product. A batch-fabrication procedure for the RGT is demonstrated and theory and experiment corroborated. Both single- and multiple-pole pair band pass filters are fabricated and discussed. Temperature coefficients of frequency as low as 90- 150 ppm/°C for the finished batch-fabricated device were demonstrated.