This brief proposes a third-order active notch filter for an interferer-rejection (IR) ultrawideband low-noise amplifier (LNA) in a 0.18-mu m complementary metal-oxide-semiconductor process. The design formulas are derived by considering the minimum power dissipation for the active notch filter that provides proper selections of the device size, the bias conditions, and the values of LC resonator. The active notch filter was then incorporated into a wideband common-gate LNA as an IR-LNA. The measurements show that the IR-LNA achieves a maximum gain of 14.7 dB, a minimum noise figure of 5.3 dB, an IR ratio of 35.7 dB, and an input third-order intercept point of -2.5 dBm at a 16-mW power dissipation, while the active notch filter rejects the interfering signal at 5.8 GHz. The chip area is 0.51 mm(2), including testing pads.
IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS II-EXPRESS BRIEFS