The next experiment we want to discuss is how to study the common emitter NPN transistors characteristics. There are three different characteristics. One for the input wherein we measure the input impedance using this formula. There is an output characteristics set of course from which the output impedance is bound out and then using the transfer characteristics of the current. The circuit diagram is shown here. This is a symbol for the transistor which has three parts, base, collector and emitter. The emitter is usually indicated with an arrow mark and for an NPN transistor the arrow mark is put out or shown outputs. The micrometer is needed to measure the base currents. A voltmeter is used to measure the base emitter voltage VBE. The battery is needed and the varying voltage source is needed to measure the input characteristics.