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Unformatted text preview: ME 530.241: Electronics and Instrumentation Lab 6: Op-Amp Applications Louis L. Whitcomb and Kyle B. Reed * Department of Mechanical Engineering The Johns Hopkins University Spring 2009 Apparatus: Multimeter, DC Power Supply, Tektronix TDS220 oscilloscope and manual, Tek- tronix CFG 253 function generator and manual, Leads, Breadboard Components: OPA544 Power Op-Amp, INA111 Instrumentation Amplifier, LF411 Op-amp, resistors, thermistor 1 Pre-Lab Exercises 1. Exercise 8.19 of . 2. Exercise 8.44 of . 3. Read all the steps in this lab. 4. Draw the connections and components for the circuit shown in Figure 3 using the pin connec- tion diagrams shown in Figure 2. Drawing this as clearly as possible will help you construct the circuit in lab. 2 Instrumentation Amplifiers and Thermistors 1. Thermistors exhibit a large negative temperature coefficient (NTC) or positive temperature coefficient (PTC) where the resistance varies as a logarithmic function of temperature. The thermistor you are using nominally exhibits a 1KΩ resistance at 25 ◦ C. With the thermistor at room temperature, check its resistance with your voltmeter. Note how the resistance changes when you touch the thermistor with your hand. 2. Analyze the circuit shown in Figure 1. Derive the formula for i out as a function of V in and R 1 . Show your work. Note: this computation may be redudant with previous labs you have done before; that is okay. 3. For the case of V in =5V, determine the value of R 1 required to result in i out = 1 mA. * c 2009 Kyle B. Reed, Louis L. Whitcomb, and Noah J. Cowan – do not reproduce without permission. 1 + Node 2 1K Thermistor OPAMP-A Node 1- Figure 1: Thermistor Circuit 4. Construct the circuit shown in Figure 1 using a provided 1K thermistor, an LF411 op-amp (OPAMP-A in the figure), and an appropriate resistor. Note that you will need the following FOUR voltage levels to construct your circuit: • +15V • +5V • 0V (connect 0V to ground) •-15V Be careful with your circuit layout. Use the power distribution rails on the prototype board to distribute these power supply connections.to distribute these power supply connections....
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- Spring '09
- Mechanical Engineering