A transistor consists of an emitter, base, and collector. Emitter and collector are semiconductors with the same type of conductivity (for example, p-type), base – with a different type of conductivity (for example, n-type). A direct voltage is applied to the emitter-base junction, the resistance of this junction is small, the current flows freely through it. The base-collector transition is reverse, the resistance is high, and since the base is thin enough, the current in the collector and emitter is approximately equal, therefore, the voltage in the collector circuit is much higher than the voltage in the emitter circuit. The transistor can be used to amplify the voltage.
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