The Charge Controlled Concept in the Form of Equivalent Circuits, Representing a Link Between Classic Large Signal Diode and Transistor Models

Three basic approaches are generally used to obtain descriptive largesignal models for transistors and diodes, the Ebers-Moll model,1 the Linvill model2 and the charge-control concept3 after Beaufoy and Sparkes. The Ebers-Moll transistor model 1,4 is based on the idea of superimposing a "normal" and an "inverse" transistor. Semiconductor junctions are represented by means of diodes and capacitors, whereas the properties of the transistor base are represented by frequencydependent current sources. The Ebers-Moll transistor model is the 523 524 T H E BELL SYSTEM T E C H N I C A L J O U R N A L , MARCH 19(57 most popular of all transistor models since it lends itself most readily to simple "rule-of-thumb calculations." The current relations are described in the frequency domain, whereas the junction voltages are described as functions of current in the time domain, or, as in the original paper, only at dc. The model simulates only the effect which minority carrier storage exercises on the relations among the various device currents, but not the effect on current-voltage relations. Since the diode is a one-port device, no diode model of the Ebers-Moll type exists that could simulate carrier storage.* The Linvill model 2,5-1,1 is almost a direct representation of the continuity and diffusion equations for semiconductor materials. It uses physical rather than circuit parameters and is superior to any other model when it comes to incorporating second-order physical effects or symbolizing new structures.