ABSTRACT
Digital signal processing (DSP) systems require interfaces to the analog world. The first amplification stage in a radio receiver is typically the tuned low-noise amplifier (LNA), which provides enough amplification to the input signal to make further signal processing insensitive to noise. Although the primary goal in LNA design is to minimize the system noise figure, the LNA must also meet other equally important specifications in gain, linearity, power consumption, input and output impedance matching, and bandwidth. In integrated circuit LNAs, the designer can control the optimum noise impedance and bias current of the input transistor by adjusting its emitter length. A bond wire is used to connect the LNA input to an off-chip antenna. Traditional LNA design employed lossless reactive components to transform the signal source impedance to the optimum noise impedance of a transistor biased at optimum minimum noise figure current density.
