Inductors are extensively used in the design of radio-frequency circuits. In the last decade, the integration of passive components, especially inductors on silicon chips, has led to the widespread development and implementation of Radio Frequency Integrated Circuits (RFICs) in CMOS technologies. However, on-chip passive inductors occupy a large silicon chip area and hardly scale down with technology scaling. Therefore, on-chip passive inductors become formidable obstacles to the realization of highly dense RFICs to be integrated with other highly dense digital circuits on a single chip using a common fabrication process. In recent years, researchers have focused on replacing passive inductors with transistor-only active circuits, namely active inductors. Active inductors can be realized with only a few transistors, which scale down with technology scaling. Therefore, they occupy a fraction of the chip area of their passive counterparts, and can be implemented densely in CMOS processes. Unlike passive inductors, bias dependent operations of active inductors allow for the tuning of their inductance and quality factor Q, and in turn, tuning the performance parameters of RFICs. This thesis focuses on the design and development of passive inductorless CMOS RFICs for ultra-wideband (UWB) receiver front-ends using active inductors. A new Q-enhanced and a new bandwidth-extended tunable active inductors are designed. Using the Q-enhanced active inductor, two tunable UWB low-noise amplifiers (LNAs) (two-stage and three-stage UWB LNAs), a UWB mixer and a wideband local-oscillator (LO) driver are designed. Active inductors are utilized to develop a novel wideband active shunt-peaking technique that decreases high-frequency losses to yield a flat gain over a wide bandwidth. A tunable multiband-UWB front-end integrating a two-stage UWB LNA, and a pair of UWB mixers driven by a pair of wideband LO drivers, is fabricated in a 90nm digital CMOS process. The passive inductorless two-stage UWB LNA, three-stage UWB LNA and UWB front-end occupy chip areas of only 0.0114mm2, 0.0227mm2, and 0.1485mm2, respectively. The active CMOS UWB front-end exhibits a measured flat gain of 22.5dB over 2.5-8.8 GHz bandwidth, and its tunability allows for varying the gain and bandwidth. / Integrated Circuits and Systems

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