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A novel fast switching noise-cancelling low-noise amplifier (LNA) is presented in this paper using 0.13-μ m CMOS for 3.1-10.6-GHz ultra-wideband applications. A new noise-cancelling topology is employed to simultaneously achieve a sub-4-dB flat noise figure and a high gain of 16.6 dB for frequencies up to 10 GHz. Fast on and off power switching is achieved by bypassing the large dc-bias resistors that lead to long charging time constants, allowing the output voltage to settle within only 1.3 ns for switching frequencies as high as 200 MHz. The phase noise and jitter added by the switched LNA was characterized, and the measured output integrated rms jitter is about 750 fs from 10 Hz to 1 MHz, while the input integrated rms jitter is 420 fs. The circuit consumes 18 mW of dc power in the on state. When the circuit is switched on and off with a 50% duty cycle, the power consumption is less than 10 mW. It occupies an active chip area of less than 0.5 mm2 .