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Using G4FETs as a Data Router for In-Plane Crossing of Signal Paths

NASA’s Jet Propulsion Laboratory, Pasadena, California
Wednesday, August 01 2007
Page 2 of 2

Figure 2. The DC Configuration of the G<sup>4</sup>FET ofFigure 1 is helpful in understanding the ability ofthe device to function as a router.
Figure 2. The DC Configuration of the G4FET ofFigure 1 is helpful in understanding the ability ofthe device to function as a router.
Figure 2 schematically shows the DC configuration of the G4FET relevant to its use as a signal router. The drain (D1) of the inversion-mode p-channel MOSFET is biased to VD1, the drain (D2) of the accumulation- mode n-channel MOSFET is biased to VD2, and the source terminals (S1 and S2) of both transistors are grounded. The two drain currents, ID1 and ID2, are perpendicular to each other and can flow at the same time. ID1 depends on minority charge carriers and flows at the surface in the x direction, while ID2 depends on majority carriers and flows at the mid-depth of the silicon film in the y direction. Surface holes and bulk electrons do not recombine because frontgate- induced depletion region isolates them. The top gate can modulate both drain currents — ID1 through regular MOS action and ID2 through verticaldepletion- width modulation. ID1 and ID2 can also weakly modulate each other — an undesirable effect in that it results in some cross-talk. In operation of the G4FET as a router, S1 and S2 would be disconnected from ground and signals would be applied to D1 and D2 for the purpose of coupling them to S1 and S2, respectively. In experiments on a G4FET that had not been optimized for use as a router, square-wave signals of various frequencies from 1 kHz to1 MHz were applied to D1 and D2 simultaneously and were shown to be coupled to S1 and S2, respectively, as desired. Crosstalk was observed, but was found to be within conventional noise margins. This result supports the expectation that the integrity of digital signals could be preserved when using G4FETs as routers.

This work was done by Amir Fijany, Farrokh Vatan, Mohammad Mojarradi, Nikzad Toomarian, Travis Johnson, Elizabeth Kolawa, Benjamin Blalock, Sorin Cristoloveanu, Suheng Chen, and Kerem Akarvardar of Caltech for NASA’s Jet Propulsion Laboratory. In accordance with Public Law 96-517, the contractor has elected to retain title to this invention. Inquiries concerning rights for its commercial use should be addressed to: Innovative Technology Assets Management JPL Mail Stop 202-233 4800 Oak Grove Drive Pasadena, CA 91109-8099 (818) 354-2240 E-mail: This e-mail address is being protected from spambots. You need JavaScript enabled to view it Refer to NPO-41827, volume and number of this NASA Tech Briefs issue, and the page number.


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