The Pospieszalski noise model and the imaginary part of the optimum noise source impedance of extrinsic or packaged FET's

The imaginary part X-Sopt of the optimum noise impedance for extrinsic or packaged devices is investigated, The analysis modifies the well-known Pospieszalski noise model by applying a series feedback to the source port, A simple expression for X-Sopt is developed and is verified for extrinsic and packaged devices with a decreasing level of accuracy, The results give further insights into the way the parasitic inductors L-g and L-s affect the noise performance of the transistor and can help to design low-noise amplifier with simultaneous signal and noise power match at the input port.