ENGI 241
LABORATORY EXERCISE 4
SUPERPOSITION THEOREM
PURPOSE
There are some powerful network theorems that allow us to easily analyze complex circuits. The
Superposition Theorem allows us to determine a load voltage or current by analyzing the effects of
each source acting independently. The purpose of this experiment is to verify this network theorem.
EQUIPMENT AND PARTS REQUIRED
1
Powered Protoboard
2
Fluke Model 37 DVM
1
Resistor 1/2 W, 5%, 470Ω, (2 each) 1kΩ, (2 each) 2.2kΩ
SUPERPOSITION
The Superposition Theorem may be employed whenever there are multiple sources in the circuit. To
use Superposition:
1.
Remove all sources but one. Voltage sources are replaced by a short and current sources are
replaced by an open.
2.
Calculate the node voltage or current.
3.
Repeat for all other sources one at a time.
4.
Algebraically sum all the individual voltages or currents.
PROCEDURE
1. Measure and record the values for all the resistors in
Table 4−1.
2. For Figure 4−1, with VS1 and VS2 at 15V, calculate
the value for VAB and IT for both load resistors using
the Superposition Theorem and record as calculated
values in Table 4−2. Determine the algebraic sum of
VAB and IT, record the sum in the Source Removed
None row.
3. Build the circuit of Figure 4−1 using RL1 as the load
resistor. Adjust VS1 to +15V and VS2 to −15V.
Measure VAB and IT and record in Table 4−2 in the
NONE removed cell.
FIGURE 4−1
4. Remove power. Open VS1 and replace with a short.
Reapply power. Measure VAB and IT and record in the appropriate cell of Table 4−2.
5. Remove power. Reinstall VS1 in the circuit, remove VS2 and replace with a short. Measure VAB
and IT and record in the appropriate cell Table 4−2.
6. Algebraically add IT and VAB and record in the SUM cells of Table 4−2. In your discussion,
compare these calculated values to the measured values. Discuss if the Superposition Theorem is
verified.
7. Repeat step 3 through 6 for RL2.
8. Perform a PSpice Bias Point analysis for the six circuit variations of Figure 4-1 (VS1 removed,
VS2 removed, both sources present). Record your output in Table 4-2. In your discussion,
compare the calculate values, the measured values, and the simulated values for VAB and IT.
Page 1
ENGI 241
LABORATORY EXERCISE 4
SUPERPOSITION THEOREM
EQUIPMENT LIST
Device
Power Supply
DVM 1
DVM 2
BCC ID #
R1
R2
R3
RL1
RL2
.47kΩ
2.2kΩ
1kΩ
1kΩ
2.2kΩ
Resistor
Rated Value
Measured Value
TABLE 4-1
Load
Source
Removed
Calculated
IT
Measured
VAB
IT
NONE
RL1
VS1
VS2
SUM
NONE
RL2
VS1
VS2
SUM
TABLE 4-2
Page 2
VAB
PSpice
IT
VAB