电气工程及其自动化专业英语section 2-4.ppt

* Chapter 2 Electronics Section 4 Operational Amplifiers Text New Words and Expressions Exercises End Translation of Long Sentences Section 4 Operational Amplifiers Introduction Operational amplifiers are high-gain difference amplifiers, which were perfected during World War II. They became the foundation of analog computers, at one time analog computers were called differential analyzers because they are used to solve differential equations. Operational amplifiers are also the basis of many important instruments. Section 4 Operational Amplifiers The analog amplifier consists of a basic difference amplifier, implemented by feedback and other compensating amplifying circuits to give linear response, stability, freedom from drift, and other desirable properties. The complexity is required because operational amplifiers amplify dc as well as ac signals, capacitive coupling between amplifying stages is not permitted. Thus it is more difficult to isolate the long-term changes that arise from variations in temperature and power-supply voltage and from other effects that cause the output voltage to drift. Section 4 Operational Amplifiers After the invention of the transistor, solid-state operational amplifiers were introduced as integrated circuits. Now operational amplifiers are used to make high-quality, low-power analog amplifier, and it is possible to avoid designing individual transistor amplifier stages for many application. For most amplifying purposes and for many measuring and control applications, simple arrangements of operational amplifiers with feedback circuits will meet the designers needs. The availability of operational amplifiers as integrated circuits in the Section 4 Operational Amplifiers form of dual in-line packages (DIPs) or in other compact forms makes the solution of analog signal problems analogous in many respects to the solution of digital logic problems, that is, through the interconnection of integrated circuit