Lab 4 - Lab4Notes Prelab:

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Lab 4 Notes Prelab: Only Parts 1, 2, and 3 will be graded. You are encouraged, but not required, to attempt all parts. Use uA741 for the op amp in all PSpice exercises. If, you decide to try Part 4, note that the photo resistors have changed to PerkinElmer Optoelectronics VT90N1. The resistance corresponding to ambient room illumination is 1 kOhm and the resistance under dark conditions is 25 kOhms. Experiments: Only Part 3 will be graded. You are not required to attempt all parts. If you attempt Part 4, see note above about the photo resistor.

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ECE 220 Lab 4 revised July 2008 © by R. N. Strickland 1 ECE 220 Lab 4 Operational Amplifiers Difference Amplifier, Light Meter This lab introduces you to the µ A741 op-amp. Two op-amp circuits will be constructed and tested: (1) difference amplifier; (2) light meter. The PSpice exercises, which form the bulk of the prelab, examine the inverting amplifier in addition to the above circuits. Instrument skills to be reinforced are: Measuring dc voltage using the oscilloscope Measuring the amplitude and frequency of ac voltage waveforms using the oscilloscope. Prelab & PSpice Exercises (30 pts) PRINT ALL PSPICE SCHEMATICS Sinewave measurements : Definitions of peak value, peak-to-peak value, and rms value are shown below. 0 10 20 30 40 50 60 70 80 90 100 -1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1 RMS value = Peak ÷√ 2 Peak-to-peak value in this case is 2V. Peak-to-peak = 2 × Amplitude Peak = Amplitude = 1V RMS = 0.707 V PSpice note : You will use transient analysis to view ac waveforms, as described in Part 1 below. Space for notes:
ECE 220 Lab 4 revised July 2008 © by R. N. Strickland 2 + - Vpos 15V 0 0 + R1 12k + R2 V _ RL 10k + - + Transient Analysis Vi AMPLITUDE = 7V FREQUENCY = 100 0 0 Vo + - Vneg -15V U1 uA741 3 2 7 4 6 1 + - V+ V- OUT OS1 OS2 0 13k 39k 43k Fig. 1 Inverting amplifier. The PSpice schematic has been set up to do a transient analysis. Running PROBE will produce oscilloscope-like plots of the input and output voltages. Part 1: Inverting amplifier with sinewave input Create the PSpice schematic 1 shown in Fig. 1. Print the schematic. The two voltage markers can be placed using the small “V” icon at the top of the screen and will automatically invoke PROBE, the PSpice plotting program, and will plot the waveforms at these nodes after the circuit simulation. Before simulating, select PSPICE/NEW SIMULATION PROFILE from the PSpice toolbar. Name the simulation profile. Once in the profile select TIME DOMAIN (Transient) under Analysis Type. Check GENERAL SETTINGS if it is not checked. Enter RUN TO TIME 20ms and enter MAXIMUM STEP SIZE 1us. The input sinusoid v i is created using the part VSIN. After placing this part double click AMPLITUDE= and FREQUENCY= and enter 1V for amplitude and 100 (this is in Hz) for frequency. Run the simulation (four times) with the following values of AMPLITUDE: 1, 3, 5 and 7V. (These are peak values.) Explain the form of the output voltage waveform across R L for each value of the input peak AMPLITUDE. Print the plots for the cases AMPLITUDE = 1 and AMPLITUDE = 7V, but first use TRACE/CURSOR/DISPLAY from the

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This note was uploaded on 05/23/2010 for the course ECE 220 taught by Professor Strickland during the Spring '08 term at Arizona.

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Lab 4 - Lab4Notes Prelab:

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