MODELING THE CHANNEL-LENGTH MODULATION COEFFICIENT FOR JUNCTION FIELD-EFFECT TRANSISTORS

The saturation current-voltage characteristics of a junction field-effect transistor (JFET) are influenced by the effective conducting channel length of the device. The effective channel length is modulated by the gate voltage and the drain voltage due to the variation of the thicknesses of the depletion layers associated with the top- and bottom-gate of the JFET. For a given gate voltage, the effective channel length will shrink if the drain voltage is increased, a mechanism normally described by the channel-length modulation coefficient lambda. This paper develops a model for calculating lambda, when combined with a recently developed JFET static model, this lambda model can be used to predict the saturation behaviour of JFETs. Experimental data are included in support of the model.