ELEC 101, Spring 2005
Prof. Rich Kozick

## Homework 5

Date Assigned: Monday, February 14, 2005
Date Due: Thursday, February 17 (pre-lab activities in item 2) and Friday, February 18, 2005 (items 3-6)

1. Reading: Please continue to study Chapter 2 in the Bobrow text: Section 2.4 (op amps), Section 2.5 (Thevenin equivalent circuit), and Section 2.6 (superposition).

2. Before lab on Thursday, February 17, please read the Lab 5 handout and do the pre-lab activities in your lab notebook.

3. Please solve problem 2.35 in the Bobrow text. Show the steps that you use in your analysis.

4. Design an op amp circuit such that the output voltage is one-fourth the input voltage, i.e.,
vo = 0.25 vi. (Hint: You may need more than one op amp.)

5. Specify an op amp circuit whose output voltage is the average of three input voltage sources:
vout = (va + vb + vc)/3. Specify values for all resistors in your circuit diagram.

6. Consider the electronic ohmmeter shown below. To use the ohmmeter, an unknown resistance R is connected as shown, and then the value of R is obtained by measuring the voltage vo and then computing R = -1000 vo.

[CIRCUIT DIAGRAM IS NOT AVAILABLE IN HTML DOCUMENT.]

• Since vo is always within the range -10 volts to +10 volts, what is the maximum value of R that can be measured with this circuit?
• How can the circuit be modified in order to measure resistance values up to 100 k ohms? Explain the reasoning behind your modification, and explain how the value of R is computed from vo in your circuit.
Thank you.