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1、电子信息类专业英语,http:/,机械工业出版社同名教材配套电子教案,温丹丽 高源 制作,Passage One Diode and Transistor,机械工业出版社 http:/,What is forward bias? What are the electrical properties of junction or diode? What are the arrangements of two-junction transistor?,Passage One Diode and Transistor,机械工业出版社 http:/,Words and Expressions diod
2、e 5daiEud n. 二极管 electron i5lektrRn n. 电子 semiconductor 5semikEn5dQktE n. 物半导体 positive 5pCzEtiv a. 电阳的 negative 5neEtiv a. 负的，阴性的 neutralize 5nju:trElaiz v. 压制 junction 5dVQNkFEn n . 连接，汇合处 terminal 5tE:minl n. 接线端,Passage One Diode and Transistor,combine kEm5bain v. (使)联合，(使)结合 polarity pEu5lAriti
3、 n. 极性 microampere 9maikrEJAmpeE(r) n. 电微安培 rectifier 5rektifaiE n. 整流器 boundary 5baundEri n. 边界，分界线 anode 5AnEud n. 电阳极，正极 emitter i5mitE n. 发射器 leakage current 漏电流 bipolar transistor 双极晶体管,Passage One Diode and Transistor,Text1. PN Junction ( Diode),When a free electron meets a moving hole in a se
4、miconductor material, the electron occupies the free space and a positive or negative charge no longer exists; that is, the charge is neutralized. When a P-type and a N-type crystal are joined to make a single semiconductor, as shown in Fig.1-1, current will flow in one direction only. As an example
5、, when a power source is connected to the semiconductor as shown in Fig.1-2, the semiconductor is said to be forward biased.,Passage One Diode and Transistor,Fig.1-1 The basic crystal junction,Passage One Diode and Transistor,Fig.1-2 Forward biased connection in,Passage One Diode and Transistor,The
6、holes will be repelled toward the junction by the positively charged battery terminal, whereas the electrons are pushed toward the junction by the batterys negative terminal.,Passage One Diode and Transistor,At the junction, the electrons combine with the hole. Electrons enter the semiconductor at t
7、he N terminal to replace the electrons that have combined with the holes. Likewise, electrons leave the P terminal by attraction of positive voltage and create new holes. This movement of electrons, from the negative voltage source through the junction and from the positive terminal of semiconductor
8、 to positive voltage source, creates a current flow. Thus current will flow in a semiconductor when the semiconductor is forward biased,Passage One Diode and Transistor,When the polarity of the power source is reversed, the semiconductor is said to be reverse biased. The holes are moved away from th
9、e junction by the negative voltage, whereas the electrons are drawn the junction by the positive voltage. Thus there is little or no combining of electrons and holes at the junction, and no current will flow.,Passage One Diode and Transistor,In practical terms, there will always be a few electrons a
10、nd holes near the junction, allowing a very small current to pass. This small current is known as leakage current and is usually in the order of a few microamperes (or possibly pico amperes). When P-type and N-type regions are formed in same crystal, the semiconductor is known as a diode or rectifie
11、r. The boundary between the two regions is termed a junction. The P-region terminal is called the anode, whereas the N-region terminal is called the cathode.,Passage One Diode and Transistor,Usually, when such semiconductors are used with signals, the semiconductors are called diodes or signal diode
12、s. When the device is used for conversion of alternating current (AC) to direct current (DC), the semiconductor is called a rectifier.,Passage One Diode and Transistor,2. Basic Two-junction or Bipolar Transistor Like a diode, a transistor can be used to prevent (or limit) the flow of current in one
13、direction, The prime use for a transistor, however, is to control the amount of current in a circuit, This is done by adding a second junction to the basic diode junction, discussed in the above section. For this reason, such transistors are called two-junction transistors or, possibly, bipolar tran
14、sistors. The author prefers the former term but recognizes that the latter term is also in common use.,Passage One Diode and Transistor,There are two possible arrangements for the two-junction in transistors: NPN, where a positive semiconductor material (holes) is placed between two negative semicon
15、ductor materials (electrons), and PNP, where the negative material (electrons) is placed between two positive materials (holes).,Passage One Diode and Transistor,With either junction arrangement, the basic two-junction transistor will have three elements. These elements, shown in Fig.1-3 as an NPN arrangement are the emitter, which emits electrons；the collector, which collects electrons; and a base, which controls the flow of electrons by controlling the charge concentration at the two-junction on either side of the base.,Passage One Diode and Transistor,Passage One Diode and Transist
