![]() Bipolar Junction Transistor Modes of Operation Holes are a minority carrier when they are in an n-type material, and electrons are a minority carrier when they are in a p-type material. For instance, a PNP transistor functions by injecting holes into the base, where they are the minority carrier whereas an NPN transistor injects electrons into the base. The term ‘minority carrier’ means that the primary contributor to current is the charged particle with the opposite polarity of the free charges in the base. They allow the BJT to function primarily via minority carrier diffusion from the base to the collector. These factors reduce carrier recombination in the base. Third, the base is very lightly doped compared with the emitter, which is the most heavily doped region of a BJT. Second, the base is much narrower than the n-type region in a standard P-N junction diode. First, the base is one single region, whereas the middle region of the two diode model is two distinct regions connected by a conductor. In particular, the base of both PNP and NPN diodes is very different from the ‘middle region’ of the two diode model. PNP TransistorĪlthough the ‘two diode model’ is good starting point for understand BJTs, it does have some limitations. In PNP transistors, the primary charge carriers are holes. In NPN transistors, the primary charge carriers are electrons.In PNP transistors, current flows from the emitter to the collector. In NPN transistors, current flows from the collector to the emitter.PNP and NPN transistors are very similar in theory of operation and construction, but there are a few fundamental differences: Since there are two sides of a P-N junction, there are two ways that a BJT can be arranged PNP and NPN. Two Types of Bipolar Junction Transistorīipolar junction transistors (BJTs) can be thought of as two PN junctions that are placed back to back. This is in contrast with unipolar devices like field effect transistors (FETs), which use only one type of charge carrier (either electrons or holes) and move through a channel that is either n-type or p-type. As current passes through the transistor, both n-type and p-type materials contribute to electric current. Common collector What Makes a Transistor Bipolar?īipolar junction transistors are called bipolar because they use both electrons and holes to conduct.Bipolar Junction Transistor Modes of Operation.Testing an NPN Transistor With a Multimeter.Testing a PNP Transistor With a Multimeter.Testing a Bipolar Junction Transistor With a Multimeter.Two Types of Bipolar Junction Transistor.Capacitor Charge, Discharge and RC Time Constant Calculator.Metal Oxide Semiconductor Field Effect Transistors (MOSFETs).Capacitors and Capacitor Circuits Menu Toggle.Resistors and Resistor Circuits Menu Toggle.Introduction to DC Circuits Menu Toggle.Module 2: Fundamental Concepts Menu Toggle.Module 1: Introduction to Electrical Theory Menu Toggle.
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