Use of the overdrive voltage in the design of an internally matched MMIC low noise amplifier

A method of biasing low noise amplifiers using the concept of overdrive voltage, V_od is introduced. The RF parameters of different FET sizes are measured against V_od to determine the optimum biasing points for good noise figure and OIP3. It was determined that the best biasing for low noise figures is between 0.15 to 0.25V and for OIP3 is 0.28 to 0.32V. Through careful selection of the biasing architecture, this concept is then applied to the design of a low noise amplifier employing a source degeneration technique. This resulted in the design of Mini-Circuit´s PSA4-5043+ broadband low noise MMIC amplifier which is internally matched and having a typical noise figure of 0.65dB at 1 GHz and 0.9dB at 4GHz using a 0.5um pHEMT process.