<P> The Early effect, named after its discoverer James M. Early, is the variation in the effective width of the base in a bipolar junction transistor (BJT) due to a variation in the applied base - to - collector voltage . A greater reverse bias across the collector--base junction, for example, increases the collector--base depletion width, thereby decreasing the width of the charge carrier portion of the base . </P> <P> In Figure 1, the neutral (i.e. active) base is green, and the depleted base regions are hashed light green . The neutral emitter and collector regions are dark blue and the depleted regions hashed light blue . Under increased collector--base reverse bias, the lower panel of Figure 1 shows a widening of the depletion region in the base and the associated narrowing of the neutral base region . </P>

The early effect in a bjt is caused by