A widely tunable narrowband balun-LNA with integrated filtering

A cascode balun-LNA with integrated out-of-band filtering for radio applications between 300 MHz and 1 GHz is proposed. First the high-Q bandpass filter (BPF) and the low noise amplifier (LNA) are analyzed, separately, in order to understand its characteristics and how both circuits can operate together. To allow maximum out-of-band interferers attenuation a single-ended and a differential filters are used in LNA, at the input and at the cascode devices, respectively. Using standard 130 nm CMOS technology operating at 1.2 V supply voltage, we obtained a voltage gain greater than 23.7 dB, noise figure (NF) lower than 3.3 dB, IIP2 > + 22 dBm and IIP3 > -4 dBm. For out-of-band frequencies the interferers are attenuated, at least, by 14 dB relatively to the desired signals.