電子專業(yè)畢業(yè)論文外文資料及翻譯譯文--恒流源-其他專業(yè)(參考版)
2025-01-23 03:20本頁(yè)面
【正文】 venin39。s capabilities, its output voltage stays constant. An ideal voltage source provides no energy when it is loaded by an open circuit (. an infinite impedance), but approaches infinite power and current when the load resistance approaches zero (a short circuit). Such a theoretical device would have a zero ohm output impedance in series with the source. A realworld voltage source has a very low, but nonzero output impedance: often much less than 1 ohm. Conversely, a current source provides a constant current, as long as the load connected to the source terminals has sufficiently low impedance. An ideal current source would provide no energy to a short circuit and approach infinite energy and voltage as the load resistance approaches infinity (an open circuit). An ideal current source has an infinite output impedance in parallel with the source. A realworld current source has a very high, but finite output impedance. In the case of transistor current sources, impedances of a few megohms (at DC) are typical. An ideal current source cannot be connected to an ideal open circuit because this would create the paradox of running a constant, nonzero current (from the current source) through an element with a defined zero current (the open circuit). Nor can an ideal voltage source be connected to an ideal short circuit (R=0), since this would result a similar paradox of finite non zero voltage across an element with defined zero voltage (the short circuit). Because no ideal sources of either variety exist (all realworld examples have finite and nonzero source impedance), any current source can be considered as a voltage source with the same source impedance and vice versa. These concepts are dealt with by Norton39。t vary much), the load current will be independent of the supply voltage, R1 and the transistor39。 current source this way. Noheless, it is often the case that such a circuit will provide adequate performance when the specified current and load resistance are small. For example, a 5V voltage source in series with a ohms resistor will provide an approximately constant current of 1mA (177。 附件 2：外文原文（復(fù)印件） CURRENT SOURCE A current source is an electrical or electronic device that delivers or absorbs electric current. A current source is the dual of a voltage source. The term constantcurrent sink is sometimes used for sources fed from a negative voltage supply. Figure 1 shows a schematic for an ideal current source driving a resistor load. Figure 1 Ideal current sources In circuit theory, an ideal current source is a circuit element where the current through it is independent of the voltage across it. It is a mathematical model, which real devices can only approach in performance. If the current through an ideal current source can be specified independently of any other variable in a circuit, it is called an independent current source. Conversely,
試題試卷相關(guān)推薦
鄂ICP備17016276號(hào)-1