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Unformatted text preview: Page 1. INTRODUCTION 1.1 Overview 1.2 Theoretical Background 1.2.1 Ideal operational amplifier 1.2.2 Practical operational amplifier 1.2.3 Inverting operational amplifier 1 1.2.4 Frequency response of an operational amplifier 1 1.3 Objective 2 2. METHOD AND MATERIALS 2 2.1 Equipment and Components 2 2.2 Procedures 3 2.2.1 D.C. gain of the amplifier 3 2.2.2 Frequency response of the amplifier 3 3. RESULTS AND DISCUSSION 4 3.1 Results 4 3.1.1 D.C. gain of amplifier 4 3.1.2 Frequency response 4 3.2 Discussion 5 3.2.1 Why does the output voltage V O not equal zero when V I =0? Explain the possible sources that give rise to the d.c. offset. 5 3.2.2 What factor determines the V O saturation value in section 4.1? 6 3.2.3 Discuss the reasons that cause discrepancies among measured gain, nominal calculated gain and actual calculated gain. 6 3.2.4 You may have noticed that during the measurement the last digit of the Digital Multimeter reading fluctuates. Will that affect the accuracy of your results? What are the main factors determining the accuracy of your results? 6 3.2.5 Explain why the gain drops at high frequency. 6 3.2.6 Explain the “virtual ground” concept with reference to the inverting operational amplifier configuration. What are the assumptions made in the derivation of the gain equation (page 3)? What are the limitations of this concept? 6 4. CONCLUSIONS 9 5. REFERENCES 9 6. LOG SHEETS i - vi TABLE OF CONTENTS 1.1 OVERVIEW An operational-amplifier (op-amp) consists of several transistors such as the Bipolar junction transistors (BJTs) and or Field-effect-transistors (FETs); diodes, capacitors and resistors. A sophisticated integrated circuit (IC) op-amp can be fabricated on a silicon chip and is available at a low price. It is basically use for amplifying signals and for solving differential equations. It is the basis for analog computers. These low-cost high performance op-amps have radically altered the design of electronic signal processing equipment from the vacuum tubes in the nineteen forties. They are the building blocks in today 's electronic circuits. 1.2 THEORECTICAL BACKGROUND 1.2.1 IDEAL OPERATIONAL AMPLIFIER An op-amp is a direct-coupled, high-gain voltage amplifier designed to amplify signals over a wide frequency range. It has two input terminals, one output terminal and an infinitely large open loop voltage gain and is represented by the symbol in Figure 1. Figure 1 Operational amplifier symbol, showing inverting ( - ) and the noninverting ( + ) inputs The characteristics of an ideal operational amplifier are listed below. Open Loop Voltage Gain, A = infinite Output Voltage, v o = 0 when v p = v n Bandwidth, BW = infinite Input Impedance, Z I = infinite Output Impedance, Z O = 1.2.2 PRACTICAL OPERATIONAL AMPLIFIER Practical op-amps have gains in the same order as that for an ideal op-amp. In addition, they have high input impedance of the order of 1M Ω , and an output impedance of the order of 100k Ω to 1k Ω . The saturation voltage,...
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This note was uploaded on 10/18/2009 for the course ECONS 111 taught by Professor Yo during the Spring '09 term at Nassau CC.
- Spring '09