In this paper

we present a concise device physics theory for I2L family. The core of the integrated injection logic family which includes I2L

I3L

S2L

SFL

SI2L and 3JL etc.

is composed of three mutually interactive PN junctions.By making use of the’Total Number of Excess Minority Carriers"mothod

and starting from the integral form of the continuity equation

we shall relate the terminal current of I2L with the total mumber of excess carriers

which are functions of the junction voltages. The theory can be used to compute the recombination losses of various regions. The culculated results can be used to understand and to design the I2L family

and the parameters are also measurable from the circuit characteristic point of view.Taking the I2L LSI or VLSI as a single device

We can specify and measure the static input and output characteristics.It exhibits various regions of operation.For each of these various modes of operation

we can simplify the analysis

and obtain

with appropriate approximation

simple equivalent circuits

which can be used for CAD.The Eber-Moll and Gummel-Poon models are useful for junction transistors. However

these models are insufficient for three mutually interactive junctions. Especially for the dynamic behavior of I2L

it is necessary to consider the building up or decaying of the "Total Number of Excess Carriers" in the entire I2L. The charging and discharging currents are no more constants as that has been assumed in the "Charge control" theory. Simplified equations will be given for the dynamic analysis of I2L. This analysis provides useful basic principles for the device design theory and the circuit design theory.