Lateral double-diffused MOSFETs (LDMOS) are becoming more popular in RF power amplifiers for wireless communication applications. The understanding of non-linearity in LDMOS is critical in order to design ultra-linear power amplifiers to meet the stringent needs of current wireless systems. We have developed a compact large signal model that can predict accurately the transconductance of the device and its higher order derivatives. Such large signal model is needed in the accurate simulation of non-linear circuits. Our device measurements show that the higher order derivatives of the transconductance are very sensitive to the gate bias. The model has been applied to simulate the gain and third order intermodulation distortion in a RF LDMOS amplifier, and the simulated results agree well with the experimental measurements. (C) 2002 Elsevier Science Ltd. All rights reserved.