Graphene is a promising candidate in analog electronics with projected operation frequency well into the terahertz range. In contrast to the intrinsic cutoff frequency (f) of 427 GHz, the maximum oscillation frequency (f) of graphene device still remains at low level, which severely limits its application in radio frequency amplifiers. Here, we develop a novel transfer method for chemical vapor deposition graphene, which can prevent graphene from organic contamination during the fabrication process of the devices. Using a self-aligned gate deposition process, the graphene transistor with 60 nm gate length exhibits a record high f of 106 and 200 GHz before and after de-embedding, respectively. This work defines a unique pathway to large-scale fabrication of high-performance graphene transistors, and holds significant potential for future application of graphene-based devices in ultra high frequency circuits.
A 900 MHz low-noise amplifier (LNA) utilizing three monolithic transformers to implement on-chip tuning networks and requiring no external components has been integrated in 2.88 mm 2 in a standard digital 0.6 m CMOS process. A bias current reuse technique is employed to reduce power dissipation, and process-, voltage-, and temperature-tracking biasing techniques are used. At 900 MHz, the LNA dissipates 18 mW from a single 3 V power supply and provides 4.1 dB noise figure, 12.3 dB power gain, 0 0 033.0 dB reverse isolation, and an input 1-dB compression level of 0 0 016 dBm. Analysis and modeling considerations for silicon-based monolithic transformers are presented, and it is shown that a monolithic transformer occupies less die area and provides a higher quality factor than two independent inductors with the same effective inductance in differential applications. I. INTRODUCTION F INE-LINE CMOS technology easily provides high frequency active devices for use in RF applications (e.g., 800 MHz-2.4 GHz), but high quality passive components (e.g., inductors) present serious challenges to integration as exemplified by several recently reported CMOS RF low-noise amplifier (LNA) designs [1]-[4]. Although significant progress toward the integration of high quality inductors including many innovative structures and design techniques has been reported [5]-[9], practical planar monolithic inductors have achieved only moderate performance owing to resistive losses in the metal traces and in the underlying substrate. Monolithic spiral transformers have been used in monolithic microwave integrated circuit and silicon radio-frequency integrated circuit designs to perform impedance matching, signal coupling, phase splitting, etc. Specific applications include low-loss feedback and single-ended-to-differential signal conversion in a 1.9 GHz receiver front end [10], and matching and coupling in an image rejection mixer [11] and in balanced amplifiers [12], [13]. In this paper, we describe a fully differential CMOS 900 MHz LNA that utilizes monolithic transformers [14]. The design is motivated by the fact that an on-chip spiral transformer comprising two coupled inductors occupies less area and Manuscript
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