Comparing the Gains of Bipolar Junction Transistor’s (BJT) using the IV characteristics of a Transistor

The bipolar junction transistor was invented by William Shockley, Walter Brattain and John Bardeen at AT&T Bell Laboratories. This three-terminal-device can function as a switch or a signal amplifier. The name ”bipolar” comes from the fact that there are two types of semiconductor materials, one positive (p) and one negative (n), through which a current flows. BJT’s are created by layering p-type and n-type silicon to form three layers. The three layers are the base, with which a small starting current is attached, the emitter, which emits electrons, and the collector, which collects electrons. There are two types of configurations: an NPN (Negative-Positive-Negative) and a PNP (Positive-Negative-Positive). An NPN switches on when a current flows through the base while a PNP switches on when there is no current through the base. The objective of this experiment is to compare the gain (href) of a NPN to a PNP by finding the Current vs Voltage (IV) characteristics of each type of transistor. The data collected from the IV characteristics will be used to extract the current gain. The current gain of transistors is crucial in electronics because when a signal amplifier is used, the maximum current output is necessary for the device being powered. To find the IV characteristics of a transistor two schematics will be made: one for a NPN and another for a PNP transistor. The PASCO Science Workshop 750 will be used to collect data. Since the PASCO 750 only has voltage sensors, the voltage over the collector resistor will be taken and then the current will be extracted using Ohm’s Law. Then the current gain will be calculated by dividing the base current by the collector current. The gain for the NPN transistor will then be compared to the PNP transistor to see which transistor has a stronger amplification.