I²L device circuit model with layout patterns

Abstract

An algorithm for CAD simulation model is discussed for an I2L circuit important for a bipolar analog‐digital hybrid LSI. A versatile modeling method is proposed here in which variation of the planar pattern of the I2L circuit is included. In this method the I2L device is divided into the injector, base electrode, collector and base termination. Each section is modeled by lumped elements consisting of transistors, diodes and resistors. the model parameters are expressed in terms of the main current density and main carrier concentration density of the I2L device. From this model, the terminal current and the carrier transit time can be related to the device shape. the terminal voltage dependence of the terminal current and the terminal current dependence of the gain bandwidth product as simulated by this method agreed within 10% with the measured values in the practical range (injector current 1 ‐ 100 μA). As an example of the application of this method to the I2L circuit, the injector current level dependence of the delay time of the 5‐stage ring oscillator and the usable current range vs. the input frequency of the 10‐stage counter are calculated and the simulation values agreed with the measured data within 10%.