This paper proposes equivalent circuit models of silicon-on-insulator (SOI) insulated-gate pn-junction devices for circuit simulations. Fundamental device models are investigated using a device simulator. The proposed equivalent circuit models of the devices utilize standard SPICE circuit elements. Equivalent circuit models are used to evaluate the performance of an electrostatic discharge (ESD) protection circuit. It is shown that the SOI insulated pn-junction devices have sufficient performance to act as ESD protection devices. By combining circuit simulations and device simulations, the high-current characteristics of SOI insulated-gate pn-junction devices are also addressed, and a couple of issues are raised with regard to the further development of these circuits. (C) 2003 Elsevier Ltd. All rights reserved.