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Lab Number 3
EEE 117L - Network Analysis Laboratory
Pre-Lab for Operational Amplifiers (Two weeks)
Assignment Week 1:
Review Chapter 5 in the text. Pay particular attention to the ideal op-amp assumptions.
Prior to the laboratory meeting make a data sheet that can be used to record all of the data that will be taken during the experiment. Using the ideal op-amp model, develop the theoretical solution for the op-amp. Solve for V 0 in terms of V 1 and V 2 as appropriate for each of the three op-amp circuits. In addition, the single input op-amp circuit should be wired on a proto-board.
Sample MultiSim circuits can be found at the following ECS server: \Voyager\EEE\EEE_
Part I - Inverting Amplifier
Read the data sheet for the LM741 on the course website.
Using the ideal op-amp model, algebraically solve for V 0 in terms of V 1. Let V 1 = 3 Vpp. Find Vo.
Derive the signal input (V 1 ) versus signal output (V 0 ) equation.
0 1
out in this circuit in
V V
Gain V V
Calculate the circuit gain.
V 1.5 Vpk0.5kHz 0°
R 1kΩ
R 1kΩ U
741
3
2
4
7
6 15 Vpos9 V
Vneg9 V
1
2
5
XSC
A B
Ext Trig+
_ _ (^) + _
3 0
4
Figure 1a. MultiSim Circuit Example
Simulate the circuit. Find the dc bias point data. Verify the circuit gain.
Part II Saturation in the Inverting Amplifier
Simulate the circuit with the input in figure 1a. = V 1 = ±10 Vpp. Discover where the LM741CN op amp saturates.
Read the LM741 data sheet. Discuss the following questions:
Does the data sheet give you any indication of how close to the power supply input voltages may the output voltage be?
Does the real op-amp deviate from the ideal model in this situation?
Part IV Weighted Summer
Using the ideal op-amp model, algebraically solve for V 0 in terms of V 1 and V 2 and the resistors. Do NOT use numeric values. Use only the algebraic symbols.
There are at least two approaches to solving this circuit.
- Use node analysis and find the output due to the two inputs simultaneously.
- Use superposition and solve for an output due solely to each input separately. For a linear, lumped parameter, time-invariant circuit, the sum of the outputs found by superposition is the complete result.
Simulate the circuit. See the lab procedure for V 1 and V 2 values. Find the dc bias point data. Plot both V 1 , V 2 and V 0 simultaneously in the time domain.
In the last part of the lab, you are asked to compare measurements made by the DMM and the oscilloscope. A brief review: The DMM measures DC and the true rms of an AC signal. It does not simultaneously report the rms value of both the DC and AC components together. The oscilloscope can be setup in many ways. While this results in a very flexible measurement device, it also introduces a number of complexities that the user must understand. DC probe coupling allows the scope to see all the components of an input signal – that is both DC and AC simultaneously. AC probe coupling allows ONLY the AC component to be seen by the scope. With this probe coupling the DC component is rejected at the scope input and is not available in the scope’s measurements.
At this point in the lab you will investigate the impact of these various settings on your measurement data. As a hint for the lab and as an aid to understand the measurements, you will now find the rms value of a sine wave with a DC offset. The rms value of a function f(t) is given by:
2 2 2 0 0
( ) ( sin ) 2
T rms (^) T f t dt VDC A d
π
Where A is the peak magnitude of the input sinusoidal voltage. Show that the rms value of a sine wave with a DC offset is:
2 2 2 2 0
( sin ) 2 2 DC DC
A
rms V A d V
π
Comment
Pre-lab (assignment week 1) is due at the start of the first Lab 3 period. The pre-lab consists of: A cover page similar to lab reports. All analysis – hand written equations ok (only for pre-lab) Screen shots of circuit simulation showing input and output waveforms as requested.
Pre-lab (assignment week 2) is due at the start of the second Lab 3 period. The pre-lab consists of: A cover page similar to lab reports. All analysis – hand written equations ok (only for pre-lab) Screen shot of circuit simulation showing input and output waveforms as specified.
