This preview shows page 1. Sign up to view the full content.
Unformatted text preview: e current in the resistor in the Tnetwork is
magnitude of the current is ⁄ ( ⁄( . The Part (d) The negative sign of associated with the current determined in Part (c) indicate that the current
flows though R from the ground into the junction of the Tnetwork. i 3 55:041 Electronic Circuits. The University of Iowa. Fall 2011.
Question 3 For the amplifier shown, determine (a) the ideal closedloop voltage gain. (b) What is the
actual closedloop voltage gain if the openloop gain is
and the opamp is otherwise
ideal? (c) What is the minimum openloop gain such that the closedloop gain is within 1% of the ideal?
(12 points) Solution
Part (a) For an ideal opamp, and so that the circuit is a follower and . Part (b) With finite openloop gain, there is a voltage difference ⁄
between the
and
Assuming
, an equivalent circuit that captures the voltages is shown in (a) below. (a) (b) Applying KVL around the loop shown in (b) gives Part (c) From part (b) we have This must be within 1% of the ideal case ( Solving yields ), or . 4 inputs. 55:041 Electronic Circuits. The University of Iowa. Fall 2011.
Question 4 Consider the follower shown below. Except for a finite openloop gain
ideal. Derive an expression for the closedloop gain. (8 points) , the opamp is Solution
With finite openloop gain, there is a voltage difference ⁄
between the
and inputs.
Assuming
, an equivalent circuit that captures the voltages is shown in (a) below. (a) (b) Applying KVL around the loop shown in (b) gives 5 55:041 Electronic Circuits. The University of Iowa. Fall 2011.
Question 5 Consider the currenttovoltage converter circuit shown. The current source has a finite
output resistance , and the opamp is ideal except for a finite openloop gain
. (a) Show that the
⁄(
input resistance indicated in the figure is given by
. (8 points) Solution
P art (a) Determining the input resistance is equivalent to determining the Thevenin equivalent resistance,
which we do as follows: turn off independent sources add a test voltage
and determine the resulting
⁄ . To turn off a current source,...
View Full
Document
 Fall '11
 Kruger
 Amplifier

Click to edit the document details