NPN transistors are good amplifying devices when the Beta value is large. The current gain of the transistor from the Collector terminal to the Base terminal is signified by Beta, ( β ). The current gain of the transistor from the Collector terminal to the Emitter terminal, Ic/Ie, is a function of the electrons diffusing across the junction. The ratio of the collector current to the emitter current is called Alpha (α). Since the physical construction of the transistor determines the electrical relationship between these three currents, (Ib), (Ic) and (Ie), any small change in the base current ( Ib ), will result in a much larger change in the collector current ( Ic ). Note: “Ic” is the current flowing into the collector terminal, “Ib” is the current flowing into the base terminal and “Ie” is the current flowing out of the emitter terminal.
The current flowing out of the transistor must be equal to the currents flowing into the transistor as the emitter current is given as A nother way to display a NPN Transistor is shown in Figure 2 below. The Base terminal is always positive with respect to the Emitter. The voltage between the Base and Emitter ( V BE ), is positive at the Base and negative at the Emitter. \): NPN Transistor schematic.įor a bipolar NPN transistor to conduct the Collector is always more positive with respect to both the Base and the Emitter.
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