Lab 5 - Lab5Notes Prelab:

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Lab 5 Notes Prelab: Only Parts 1, 2, and 3 will be graded. You are encouraged, but not required, to attempt all parts. Experiments: Part 4 will not be graded. You are encouraged, but not required to attempt all parts.
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ECE 220 Lab 5 revised July 2008 © by R. N. Strickland 1 ECE 220 Lab 5 RC/RL Waveshaping Circuits RC Timing Circuits/Comparator Circuits Integrating Op-Amp Circuit/Waveform Generator This lab concerns: (1) analysis and design involving the step and pulse response of RL and RC circuits; (2) analysis and design of the integrating op-amp circuit; (3) building a two op-amp waveform generator (integrator plus comparator-with-hysteresis); (4) designing and building an RC timing circuit with a comparator. The PSpice exercises have been integrated with the prelab. PSpice exercises are shown in bold. Instrument / circuit skills to be reinforced are: Using the function generator to trigger the oscilloscope Accurately measuring periodic waveforms on the oscilloscope Building and troubleshooting op-amp circuits. Prelab (30pts) PRINT ALL PSPICE SCHEMATICS This prelab introduces some new features of PSpice , namely: using labeled nodes to plot variables, setting initial conditions for inductors and capacitors, using a switch, and creating pulses and periodic waveforms. Part 1. Response of an RC circuit to a step input. Assume the switch in the circuit of Fig. 1 closes at t = t o . The initial capacitor voltage at t = t o is V o . Fig. 1: Circuit for observing RC step response. This is the first time we have used switches in PSpice. Notice that the default resistance between the con- tacts of an open switch is less than infinity. Likewise, the resistance when closed is > 0. Double click on the switch to investigate. Ic + (a) Write general expressions for the capacitor voltage v(t), the capacitor current i c (t), and the resistor current i R (t), in terms of I 1 , R, C, V o and t o . (See Theory on p. 7 of this document.) Where necessary, give separate expressions for t t o - and t t o +. (b) Draw the schematic of Fig. 1 in PSpice , using the components C, R, IDC and Sw_tClose. Use R=1.8k , C=0.056 µ F. Set the initial capacitor voltage to -6V by double-clicking on the capacitor and setting the parameter IC = -6. Double-click on TCLOSE= on the switch to set it to close at 0.2ms. Print the schematic. Setup PSPICE / NEW SIMULATION PROFILE / TIME DOMAIN with the parameters: run to time 1ms, and maximum step size 1 1us. Select PSPICE/RUN, and plot the capacitor voltage. (You might have to flip the capacitor if the curve starts at +6V.) Mark the curve (TRACE / CURSOR / DISPLAY Î PLOT/ LABEL/ MARK) at 0.3ms. Print the plot. Next, on the schematic, change the marker to one for the capacitor current; run the simulation and again mark the current plot at 0.3ms, and print the plot. Repeat for the resistor current.
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Lab 5 - Lab5Notes Prelab:

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