ELEC 101, Spring 1998
Prof. Rich Kozick
Homework 9
Date Assigned: Wednesday, March 4, 1998
Date Due: Monday, March 9 and Wednesday, March 11, 1998
Please do your best to solve the following problems for
Monday, March 9.
We will discuss any questions that you have in class on Monday,
and your solutions will be due on Wednesday.

Professor Aburdene will teach the class on Friday while
I am out of town.
He will introduce a circuit that will play a role
in the design project that we will do for lab next week.
This is an important class that you should attend!

Please do problem 3.28 in the text.
What is the time constant for this circuit?

Repeat problem 3.28 for the case that the switch is
opened for t < 0, and the switch is closed
for t >= 0.
What is the time constant for the circuit in this case?

Please do problem 3.48 in the text.
Note that the voltage source has value 0 volts for t < 0,
and V volts for t >= 0.
Thus it is equivalent to "closing a switch" at time t = 0
to connect an ideal source with value V volts.
Hint:
Write KCL at the "" input of the op amp.
Use the ideal op amp assumptions.
Also answer the following questions for this circuit.
 What is the time constant?
 Sketch v_{o}(t).
 After a long time, i.e., t >> 0, does this look like
an inverting amplifier? Please explain.
Thank you.