【正文】 識是有限的，所學(xué)知識還不夠豐富，在老師和 同學(xué)們的悉心幫助下，雖然我順利完成了畢業(yè)設(shè)計(jì)論文，但是我深知設(shè)計(jì)中仍有許多不足之處，希望老師們提出寶貴意見。 張 老師平日里工作繁多 ， 但在我做畢業(yè)設(shè)計(jì) 的整個過程中都給予了我悉心的指導(dǎo) 。s law but I = EEV I0 (1) of the index. When a small voltage V is added to the diode, will have a small currents, and produce a about voltage drop V, which are often thought ON the diode is the voltage drop , positive, the value for silicon diode about V. In many diode series circuit, need to consider the voltage drop, also need to consider the VON electricity flow through diode. When the diode reverse bias, generates a lot of impedance, but still exists a weak electricity. Namely, when it through the leakage current d iodes, only a few ma even a few microamps of size, usually neglected. In practical applications, must consider diode current and voltage tolerance. Allows For example, when using diode rectifier diode, requires the living must be able to reverse voltage. If not, they will choose diode can be breakdown. There are many different types of semiconductor diodes, for example, and it is often used as a diode, switch, Zener, because it has to it and reverse voltage stabilizing often in a voltage this characteristic, therefore it is often 本科 畢業(yè)設(shè)計(jì)論文 31 used to voltage, Light emitting diode, when positive offset voltages and currents, it will be light. Photoelectric diode, it depends on the size of the voltage drop in the light of its total, can use it to measure how much light, Thyristor (SCR rectifier) is a simple with conventional rectifier control signals, etc. 2. Transistors Transistor is one of the most mon in the semiconductor devices, is widely used in the electronics, mainly divided into bipolar transistors mosfet and two categories. Mainly used in semiconductor materials, sometimes use silicon germanium. People usually preferred properties of silicon, because the silicon germanium is much better than that he had better thermal stability and repeatability. A bipolar trans istor is posed by a PN junction type diode back together constitute a sandwich structure, make a N or P type semiconductor between semiconductor in another. Therefore, based on the sandwich different types of silicon, there will be NPN and two types o f PNP bipolar transistors. A bipolar transistor consists of 3, respectively for passive device identifier (B), collector (C) and emitter (E), the arrow usually indicates a transmitter. Two types of transistors, and working principle of the current direction through devices. A bipolar transistor consists of current control devices, a small role in the base current can be controlled from much of the current emitter current direction sets, Ic=β Ib, formula ofβ is current gain, scope of 20 to 200, even for a transistor, beta is not with the emitter current increases, this is because the number of electrons injected than the area can be used with the pound cavity number, so that the base current produced pound cavity part will further decrease. The transistor circuits are below four working area (1) Cut off region (no collector current), switching operation. Closed (2) Active region (a collector current workspace, and the collector voltages above a few volts) transmitter voltage, used to amplify. 本科 畢業(yè)設(shè)計(jì)論文 32 (3) Saturated region (voltages above emitter collector voltage, a few volts) can be used to produce large current switch operation. (4)Avalanche breakdown region, transistor will be broken down. 3. The power When business electronic school, the need for a power unit. Power unit by the energy from the power circuit to the load. The power of the main use is to be effective AC input power into electronic equipment required DC voltage. According to the power semiconductor devices, power supply units can be linear or switching. Linear power supply is often used for lifting and lowering blood pressure. Use external resistance, linear regulators have created a constant output voltage or variable output voltage. Linear power supply mainly contains transformers, rectifiers, filters, and voltage regulator. Transformer plug the AC from one into another voltage. Enter the winding is called a winding, output windings bee secondary winding. Between the two windings without electricity connections, replacing it with a soft by transformer core of alternating magic fields to connect them. Bridge rectifier for output DC, he can consist of four individual diode or integrated with a single four diode chips for use in a fullwave rectifier, can also be used to produce halfwave output of a diode. voltage consumed in bridge rectifier, because when each diode used , and the bridge rectifier diode is always two while conducting. Bridge rectifier is made it through maximum current value and the maximum current value and the largest reverse voltage (the voltage value at leastmeansquare voltage is the power of three times, so rectifiers to hold peak nominal voltage). With capacitors, resistors, or or inductor, or binations of them consisting of a filter you can filter portion of the pulse and smooth DC voltage. However, the filter is not a perfect, there is still a small pulse, often called 本科 畢業(yè)設(shè)計(jì)論文 33 ripple. For many circuit, ripple voltage is the power supply voltage of the 14 is appropriate. For lowcurrent power supplies, simple regulator can consist of one resistor and a reverse connection of Zener diodes. But today, many types of integrated regulator output that can be fixed (typically 5V and 12V and 15V) or variable value, this dramatically simplifies the design process. Most of the regulator has some overcurrent and overheating of the autoprotect feature. Many fixedvoltage integrated regulator has three thread looks like power transistors. They contain a hole, if necessary, in the cavity can be attached to a heat sink. The advantage