Abstract: A method of trimming the light sensitivity of phototransistors that are produced in a wafer-based semiconductor process is disclosed. The phototransistors each have a rear-side collector, a base embedded in the collector, an emitter embedded in the base, and a front-side metallization that includes at least one bond pad for the emitter, and in particular a trimming structure. The regions of the front-side covered by the metallization define a light-insensitive area of the respective phototransistor, and the metal-free regions of the front-side define a light-sensitive area of the respective phototransistor. The method includes the steps of measuring the collector-emitter current of the phototransistors, and changing, in particular increasing, the size of the light-sensitive area by changing the size of the area covered by the metallization, in particular by removing at least a part of the trimming structure, in dependence on the measured collector-emitter current.