A dual-band SiGe HBT low noise amplifier

To adapt to the rapid development of multi-standard mobile communication, a low noise amplifier (LNA) that can operate at two frequencies of 800MHz and 1.8GHz respectively was designed. SiGe HBTs with good noise performance were used in the design. The Cascode circuit topology was adopted to reduce the Miller effect of the transistor. Inductor degeneration in emitter was introduced to decouple the input impedance from the noise factor. The input matching is achieved through serial and parallel LC circuit which can resonate at two frequencies simultaneously. The output matching circuit was realized by adjusting the load impedance to 50Ω. The simulated results show that the transmission gain S
₂₁
reached 24.3dB and 21.3dB at 800MHz and 1.8GHz respectively. Both S
₁₁
reached -13dB simultaneously, Both S
₂₂
are lower than -27dB. The noise figures are 3.3dB and 2.0dB at these two frequencies respectively. Finally the layout of the monolithic integrated dual-band LNA is presented.