The extraction of GaAs MESFET intrinsic noise parameters and their variation with bias

The conventional method of noise characterisation for FET type structures, such as MESFETs and HEMTs is by the use of measured extrinsic noise parameters. These parameters being the minimum noise figure (Nfo), the complex source reflection coefficient (Γopt), which when presented to the device results in a noise figure of Nfo, and the noise resistance (Rn). To completely characterise a device these parameters must be obtained at every frequency and bias point of interest. This procedure is well documented but can be a long, tedious and often inaccurate process. A simpler technique is to make use of the device´s intrinsic noise parameters P, R and C. These parameters are frequency independent up to 30 GHz and hence can be obtained over a restricted measurement frequency range but used to characterise the device over a much wider frequency range. In this paper we discuss the extraction of the intrinsic noise parameters of a short gate-length GaAs MESFET, measured results are presented that show how bias conditions effect these parameters