BJT as a Switch DefinitionA BJT (bipolar junction transistor) is defined as a device that acts as a switch by controlling the base-emitter current to change the emitter-collector resistance.A switch creates an open circuit (infinite resistance) when in the ‘OFF’ position and a short circuit (zero resistance) when in the ‘ON’ position. Similarly, in a bipolar junction transistor, controlling the base-emitter current can make the emitter-collector resistance nearly infinite or nearly zero.In a tra