【正文】 場效應晶體管 7. proper biasing 共集電極 8. monbase 穿過 9. monemitter 正確偏置 10. moncollector 共發(fā)射極 山東信息職業(yè)技術學院電子工程系 Reading Amplifier Much as the gate abstraction forms the foundation of most of digital electronics, the operational amplifier forms the basis for much of electronic circuit design. The operational amplifier is arguably the most useful single device in analog electronic circuitry. With only a handful of external ponents, it can be made to perform a wide variety of analog signal processing tasks. It is also quite affordable, most generalpurpose amplifiers selling for under a dollar apiece. Modern designs have been engineered with durability in mind as well: several opamps are manufactured that can sustain direct shortcircuits on their outputs without damage. 山東信息職業(yè)技術學院電子工程系 The name operational amplifier originates from the bygone days of the analog puter (19401960), in which the constants in differential equations were represented by the gains of amplifiers. Thus these amplifiers, constructed from balanced pairs of specially manufactured vacuum tubes, had to have reliable, known, fixed gains. Because transistors are inherently more temperaturedependent than vacuum tubes, it was at first thought that satisfactory transistor Op Amps could not be built. But in 1964, it was discovered that by fabricating balanced transistor pairs close together on a single silicon chip to minimize thermal gradients, the temperature problems could be overe. And thus were born in rapid succession the 703, the 709, and then the ubiquitous 741. Op Amps are rarely used for analog puters now, but instead have bee universal building blocks in all aspects of analog circuitry. 山東信息職業(yè)技術學院電子工程系 The Op Amp is a multistage twoinput differential amplifier that is designed to be an almost ideal control device, specifically, a voltagecontrolled voltage source. An abstract representation of the operational amplifier shown in Fig 24suggests it is a fourport device. The four ports are an input port, an output port, and a pair of power ports. A+VSvoltage (for example, 15 volts) is applied at the plus power port and a ?VSvoltage (for example, ?15 volts) is applied at the minus power port. An input voltage (the control) applied across the noninverting and inverting input terminals of the Op Amp is amplified by a large amount and appears at the output port. In the operational amplifier abstraction, the input impedance across the input port is infinity, and the output impedance is zero. The gain, or the factor by which the input voltage is amplified, is also infinity. 山東信息職業(yè)技術學院電子工程系 The symbol and standard labeling for the operational amplifier are shown in Fig 24(a). The two required external power supplies have been explicitly shown in the diagram, although showing them is not the usual practice. All five currents have been labeled, in addition to appropriate node voltages, referred to the indicated mon ground terminal. In this primitive circuit, the voltage vi is used to control the output voltage vo. Let us examine this control function in detail to find out both the extent of the control, and the cost of the cont