Figure 1 A schematic representation of an operational amplifier is shown. For an
ideal opamp, R_{in} = infinity, R_{out} = 0, and the gain, k = infinity.
Figure 2 The inverting opamp circuit is shown in (a). The wiring diagram is shown
in (b).
Figure 3 The experimental setup is shown. A signal generator provides an input signal.
Two power supplies were used, one for +Vcc and the other for Vcc.
Figure 4 Oscilloscope trace shows a 0.6 peak input voltage.
The output saturates at V_{cc} (5V). R_{1} is 1K and R_{2} is 10k.
The gain is 10 until the amplifier saturates at +/ 5V.
The input and the output are 180 degrees out of phase.
Figure 5 The noninverting opamp circuit is shown.

Opamp Lab
Ideal Opamp
A schematic representation of an operational amplifier (opamp) is shown in Figure 1.
In most situations an opamp can be considered ideal. An ideal opamp has an infinite input resistance,
R_{in},
zero output resistance, R_{out}, and an infinite gain, k.
Since R_{out} is zero, the voltage on the output pin, V_{out}
is equal to the difference in the voltages on the input pins.
 (1) 
And since the gain k is typically greater than 10^{5} the difference between the
voltages on the input pins is approximately zero.
 (2) 
Ideal opamp rules
 The voltage on the inverting input, V^{} is equal to
the voltage on the noninverting input, V^{+}.
 No current flows into or out of the input terminals.
Rule 1 follows from Equation 2.
Rule 2 follows from the assumption that R_{in} is infinite. It is reinforced by Rule 1, since
if there is no voltage across R_{ in} no current will flow.
Inverting Opamp Circuit
The inverting opamp circuit is shown in Figure 2. The node equation for the inverting input, node A,
is,
 (3) 
No current flows into the opamp from node A. Also since the voltage at the inverting input
is equal to the voltage at the noninverting input, the voltage at node A is zero. Equation 3 becomes,
 (4) 
The gain is,
 (5) 
Noninverting Opamp Circuit
The noninverting opamp circuit is shown in Figure 5. Since both opamp input terminals are at the same
voltage, the voltage at node A is V_{in}. Since no current flows into the opamp's negative
input terminal, the same current flows in both R_{1} and R_{2}. Therefore,
 (6) 
 (7) 
Tasks
 Wire up the inverting opamp circuit shown in Figure 2. Set Vcc to 5V and Vcc to 5V.
 Use a voltmeter to measure the DC voltages applied to the opamp chip.

Apply a 1 KHz, 0.1 V (peak) signal to the inverting opamp circuit. (Set the DC signal generator output
to zero. Observe the output voltage using an oscilloscope to ensure that the opamp is not saturating.)
 Design an experiment to measure the output impedance of the inverting circuit.
 Repeat 14 for the nonverting circuit shown in Figure 5.
Questions
 What is the gain of the inverting circuit?
 What is the gain of the noninverting circuit?
 What is the input resistance of the inverting circuit?
 What is the input resistance of the noninverting circuit?
 What is the maximum output voltage?
 What is the output resistance of the inverting circuit? (The noninverting circuit will have a similar
output resistance.)