An active-balun LNA with forestage-poststage gain controls for VHF/UHF mobile-TV tuners

Presented is a novel active-balun low noise amplifier (LNA) with forestage-poststage gain controls for VHF/UHF mobile-TV tuners. It consists of two passive attenuators inter-operating with an active core to optimize the RF performances under different reception scenarios. The forestage is a MOS-based attenuator configured in a way that, at all attenuation levels, a broadband input impedance match can be obtained. The interstage is a single-to-differential amplifier exploiting a common-source common-gate structure for noise cancellation. The poststage is a capacitor (CAP)-based attenuator, which adjusts the dynamicity of the output signal before driving the mixer. With this forestage-poststage gain controls the system noise figure and linearity can be easily traded at different gain levels. Optimized in a 0.18-¿m CMOS process the LNA attains 0.85-dBm IIP3 at a maximum voltage gain of 26 dB, a 37-dB gain range with a 6-dB step size, and an average noise figure of 2.9 dB. The power consumption is 10.8 mW at 1.8 V.