Basic Electronics.pdf电路学 - 基础电路里面的元器件介绍以其例子，适合新手Se

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详细说明：电路学 - 基础电路里面的元器件介绍以其例子，适合新手Semiconductor - I Silicon is the most common material used to build semiconductor devices Si is the main ingredient of sand and it is estimated that a cubic mile of seawater contains 15.000 tons of si Si is spun and grown into a crystalline structure and cut into wafers to make electronic devices Seed crysta Boule slicon Molten wafer silicon Heated to ~2570°F Semiconductor -Il Atoms in a pure silicon wafer contains four electrons in outer orbit(called valence electrons) Germanium is another semiconductor material with four valence electrons In the crystalline lattice structure of Si, the valence electrons of every Si atom are locked up in covalent bonds with the valence electrons of four neighboring Si atoms In pure form Si wafer does not contain any free charge carriers An applied voltage across pure Si wafer does not yield electron flow through the wafer a pure Si wafer is said to act as an insulator In order to make useful semiconductor devices, materials such as phosphorus(P)and boron(b) are added to si to change si's conductivity. Silicon wafer 4 valence electrons S Atomic number Silicon atom mbo , S Si 14 Covalent bond S Si Atomic weight Si 28.086 4 sit si t si t Valance Silicon shell S Si Atomic configuration N-Type silicon Pentavalent impurities such as phosphorus, arsenic, antimony, and bismuth have 5 valence electrons When phosphorus impurity is added to Si, every phosphorus atom's four valence electrons are locked up in covalent bond with valence electrons of four neighboring Si atoms. However, the 5th valence electron of phosphorus atom does not find a binding electron and thus remains free to float. When a voltage is applied across the silicon-phosphorus mixture, free electrons migrate toward the positive voltage end When phosphorus is added to Si to yield the above effect, we say that Si is doped with phosphorus. The resulting mixture is called N-type silicon(N: negative charge carrier silicon) The pentavalent impurities are referred to as donor impurities 5 valence electrons n-type silicon 艾5 艾 P15 Electron flow Si Si 30.974 Si Si Phosphorus r EXtra electron Atomic configuration P-Type Silicon—1 Trivalent impurities e.g., boron, aluminum, indium, and gallium have 3 valence electrons When boron is added to Si, every boron atoms three valence electrons are locked up in covalent bond with valence electrons of three neighboring Si atoms. However,a vacant spot"hole 'is created within the covalent bond between one boron atom and a neighboring Si atom. The e holes are considered to be positive charge carriers When a voltage is applied across the silicon-boron mixture, a hole moves toward the negative voltage end while a neighboring electron fills in its place When boron is added to si to yield the above effect, we say that Si is doped with boron. The resulting mixture is called P-type silicon(P: positive charge carrier silicon) The trivalent impurities are referred to as acceptor impurities 3 valence electrons p-type silicon Si中Si Hole flow B 5 B si中B 10.811 Si Si S Boron Atomic configuration P-Type Silicon-I The hole of boron atom points towards the negative terminal The electron of neighboring silicon atom points toward positive terminal The electron from neighboring silicon atom falls into the boron atom filling the hole in boron atom and creating a"new hole in the silicon atom It appears as though a hole moves toward the negative terminali Diode a diode is a 2 lead semiconductor that acts as a one way gate to electron flow Diode allows current to pass in only one direction a pn-junction diode is formed by joining together n-type and p-type silicon .In practice, as the n-type Si crystal is being grown, the process is abruptly altered to grow p-type Si crystal. Finally, a glass or plastic coating is placed around the joined crysta .The p-side is called anode and the n-side is called cathode When the anode and cathode of a pn-junction diode are connected to external voltage such that the potential at anode is higher than the potential at cathode, the diode is said to be forward biased In a forward-biased diode current is allowed to flow through the device .When potential at anode is smaller than the potential at cathode, the diode is said to be reverse biased. In a reverse-biased diode current is blocked DIODE Symbol for DIODE + Water Analogy of Diodes Water-Tight Pivot Spring Movable plate Solid stor When water pressure on left overcomes the restoring force of spring, the gate is opened and water is allowed to flow When water pressure is from right to left, the gate is pressed against the solid stop and no water is allowed to flow pring restoring force is analogous to 0.6V needed to forward bias a Si diode Diode: how it works -I When a diode is connected to a battery as Hole flow Electrons shown, electrons from N the n-side and holes from Holes side are forced toward the center by the electrical field supplied the battery. The electrons and holes combine causing the current to pass through Electron flo the diode. when a diode Repels electrons is arranged in this way, it Repels holes is said to be forward biased Forward-biased (open door")

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