An analytic technique for trade-off of noise measure and mismatch loss for low noise amplifier design

An analytic technique and figure-of-merit (F_nm) for the trade-off of noise measure and mismatch loss in the design of a low noise amplifier is presented. The trade-off between various design parameters as a function of inductive source degeneration is evaluated from design curves developed and are shown to be unique to the selected device. Several devices demonstrated conditions whereby the use of source degeneration leads to instability and must be avoided. The technique is straightforward and permits pre-screening of potential devices being considered for low noise amplifier design. The resulting design curves permit accurate selection of the range of acceptable feedback values to achieve desired performance. The new figure-of-merit allows designers to choose the optimum value of source inductance either analytically or graphically. The new methodology is discussed and applied to a low noise amplifier design at 10.24 GHz.