自動(dòng)化專業(yè)外文翻譯--運(yùn)算放大器-其他專業(yè)(編輯修改稿)
2025-02-24 02:44 本頁面
【文章內(nèi)容簡(jiǎn)介】 zones), it is referred to as a bipolar device, or bipolar transistor. A transistor thus has three elements with three leads connecting to these elements. To operate in a working circuit it is connected with two external voltage or polarities. One external voltage is working effectively as a diode. A transistor will, in fact, work as a diode by using just this connection and fetting about the top half. An example is the substitution of a transistor for a diode as the detector in a simple radio. It will work just as well as a diode as it is working as a diode in this case. The diode circuit can be given forward or reverse bias. Connected with forward bias, as in , drawn for a PNP transistor, current will flow from P to the bottom N. If a second voltage is applied to the top and bottom sections of the transistor, with the same polarity applied to the bottom, the electrons already flowing through the bottom N section will promote a flow of current through the transistor bottomtotop. By controlling the degree of doping in the different layers of the transistor during manufacture, this ability to conduct current through the second circuit through a resistor can be very marked. Effectively, when the bottom half is forward biased, the bottom section acts as a generous source of free electrons (and because it emits electrons it is called the emitter). These are collected readily by the top half, which is consequently called the collector, but the actual amount of current which flows through this particular circuit is controlled by the bias applied at the center layer, which is called the base. Effectively, therefore, there are two separate 39。working39。 circuits when a transistor is working with correctly connected polarities (Fig. 12B3). One is the loop formed by the bias voltage supply enpassing the emitter and base. This is called the base circuit or input circuit. The second is the circuit formed by the collector voltage supply and all three elements of the transistor. This is called the collector circuit or output circuit. (Note: this description applies only when the emitter connection is mon to both circuits ~ known as mon emitter configuration.) This is the most widely used way of connecting transistors, but there are, of course, two other alternative configurations mon base and mon emitter. But, the same principles apply in the working of the transistor in each case. The particular advantage offered by this circuit is that a relatively small base current can control and instigate a very much larger collector current (or, more correctly, a small input power is capable of producing a much larger output power). In other words, the transistor works as an amplifier. With this mode of working the baseemitter circuit is the input side。 and the emitter through base to collector circuit the output side. Although these have a mon path through base and emitter, the two circuits are effectively separated by the fact that as far as polarity of the base circuit is concerned, the base and upper half of the transistor are connected as a reverse biased diode. Hence there is no current flow from the base circuit into the collector circuit. For the circuit to work, of course, polarities of both the base and collector circuits have to be correct (forward bias applied to the base circuit, and the collector supply connected so that the polarity of the mon element (the emitter) is the same from both voltage sources). This also means that the polarity of the voltages must be correct for the type of transistor. In the case of a PNP transistor as described, the emitter voltage must be positive. It follows that both the base and collector are negatively connected with respect to the emitter. The symbol for a PNP transistor has an arrow on the emitter indicating the direction of c
教學(xué)課件相關(guān)推薦
鄂ICP備17016276號(hào)-1