To define the parameters of the pulse we want to use, double click on the voltage source and make the following settings in the PULSE VOLTAGE settings window. We will use a special voltage source in the component library to accomplish this. For the purpose of this exercise, you will create a waveform that is 5V for the first 500ns and 0V for the next 500ns, then repeats this pattern.
You will need to define the parameters of the pulse source.
When the pulse is low (0V), it behaves as if the switch is in position 1 and when the pulse is high (5V), it behaves as if the switch is in position 2. The purpose of the pulse is to model the behavior of a switch operating between positions 1 and 2 (as in the prelab version of this circuit). Unlike in last week s simulation, the voltage source you will use today will be a 0 to 5V pulse signal (Vpulse). The capacitor can be found in the Basic group. There are two new components in this circuit that we didn t use last time. R 1 = 10kΩ V 1 + C 1 = 5pF Figure 2: It is the same circuit you analyzed in the prelab. Creating the Circuit: You will start by creating the circuit shown in Figure 2 in the Multisim workspace. You can refer back to last week s notes to refresh your memory on other portions. It is assumed that you remember (or can look up) the software procedures you used last week in Lab 3, so these instructions will focus on the new features we haven t used before. Lab Exercises The purpose of this lab is to analyze an RC network using Multisim. Plot the discharge curve using the capacitor discharge formula given in class. Assume the capacitor is fully charged, and the switch moves to position 1 at t = 0sec. Plot the charge curve using the capacitor charge formula given in class. Answer the following: (a) What is the time constant for the circuit? (b) What will the capacitor voltage be at t = 150ns? (c) What will the resistor voltage be at t = 150ns? (d) What will the resistor current be at t = 150ns? (e) How much time must pass for the capacitor voltage to reach 1V? 3. Plot the charge curve for the capacitor using the 2/3 estimation method given in class. At t = 0s, the switch moves to position 1 and the capacitor begins to discharge. For step 4, assume the switch has been in position 2 for a long time. At t = 0s, the switch moves to position 2 and the capacitor begins to charge. 1 Lab 4 Multisim Evaluation of an RC Network Prelab Exercises All graphs must be fully labeled and drawn neatly! No answers are complete without the units! as always, show your work! 2 R 1 = 10kΩ 5V + V s t = 0s 1 C 1 = 5pF Figure 1: Cicuit for prelab exercises For steps 1, 2, and 3, assume the switch has been in position 1 for a long time.
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