A bipolar junction transistor (BJT) may be used in a power stage DC-to-DC converter, such as a converter in LED-based light bulbs. The power stage may be operated by a controller to maintain a desired current output to the LED load. A resistor may be coupled to the BJT through a switch at the emitter of the BJT. The switch may regulate operation of the BJT by allowing current flow to ground through the resistor. The controller may perform measurements of the resistor to allow higher accuracy determinations of the current through the BJT and thus improve regulation of current to the LED load.