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Unformatted text preview: L2 Opamps Labs 2 and 3 concern operational amplifiers, or opamps. Opamps were originally developed to implement mathematical operations in analog computers, hence their name. Today, opamps are commonly used to build amplifiers, active filters, and bu ff ers. You will work with many of these circuits in lab. In class we discussed opamps as ideal elements. However, there are di ff erences between the ideal and practical characteristics. OpAmp Property Ideal in practice Gain A very large, 10 6 and constrained by supply voltage R i very large, 10 6 R o very small, 15 Frequency response flat gain depends on frequency The objective of this experiment is to gain experience in the design and construction of oper ational amplifier circuits. You will also examine some nonideal opamp behavior. By the end of Lab 2, you will have designed and built two amplifiers for your radio circuit. Once you have verified that they work, you will connect them to your envelope detector from Lab 1 and listen to synthetic AM signals. 1 Prelab In the prelab exercises, you will review the analysis of opamp circuits and design amplifiers for your radio circuit. 1. Assuming ideal opamps, derive an expression for the output voltage v o in each of the two circuits in Figure L2.1. Simplify your expression as much as possible. 327 L2 Opamps (a) R 4 + R 1 R 2 R 3 v o v 1 v 2 (b) R 4 + R 1 R 2 R 3 v o v 1 R 5 Figure L2.1: Circuits for prelab analysis. R 1 R 2 v o v i + Figure L2.2: Circuit for analysis and design problem. 2. Again assuming an ideal opamp, derive an expression for the output voltage v o in the circuit in Figure L2.2. a) For a gain v o v i of 2, how must R 1 and R 2 be related? b) For a gain v o v i of 11, how must R 1 and R 2 be related? c) How do you build two amplifiers, one with a gain of two and one with a gain of 11, given four resistors: one 2 k , two 10 k , and one 20 k ? d) Using the pinout diagram in Figure L2.3 as a reference, draw how you will wire the 328 L2 Opamps V CC + + V CC 1 2 3 4 8 7 6 5 Pins 1,5 o ff set null correction not used 2 inverting input () 3 noninverting input (+) 4 V CC supply set to 12 V (DC) 7 V CC + supply set to 12 V (DC) 6 output voltage v o 8 not connected Figure L2.3: Pinout diagram for the 741 opamp....
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This note was uploaded on 04/09/2010 for the course ECE 210 taught by Professor Staff during the Spring '08 term at University of Illinois, Urbana Champaign.
 Spring '08
 Staff

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