Isothermal I-V Characterization of a 75-Watt MOSFET

High-power RF devices have a growing presence in wireless communication. Unfortunately, these devices cannot be (safely) characterized by classical continuous techniques because of the large dissipated power levels that are involved and their susceptibility to bias oscillation. For that reason their characteristics are commonly predicted by scaling up smaller devices. However, traditional continuous measurements lead to scale factors that are distorted mainly by thermal effects due to the device self-heating. In this paper we propose a procedure that makes use of an isothermal measurement system to obtain, analyze and verify the scaling factors of a lateral diffused MOS transistor at ambient temperature. Among the benefits of this technique we can find the calculation of the isothermal scaling factors, the investigation of regions outside the safe operating area and the prevention of device bias oscillations.