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====== Transistor ====== {{ :neonking:transistor.jpg?direct&300 |}} ===== Introduction ===== A Transistor is a device composed of semiconductor material that **amplifies a signal or opens or closes a circuit**, like a switch. It can cause changes in a large electrical output signal by small changes in a small input signal. That is, a weak input signal can be amplified (made stronger) by a transistor. For example, very weak radio signals in the air can be picked up by a wire antenna and processed by transistor amplifiers until they are strong enough to be heard by the human ear. A transistor consists of three layers of silicon or germanium semiconductor material. Impurities are added to each layer to create a specific electrical positive or negative charged behavior. "P" is for a positive charged layer and "N" is for a negative charged layer. Transistors are either NPN or PNP in the configuration of the layers. ===== MDIBox-related ===== BC547 / BC557 / BC337 are useful references to test with
