The document discusses the superposition theorem. It defines superposition theorem as stating that the voltage or current through an element of a linear, bilateral network with multiple sources is equivalent to the summation of the voltage or current across that element generated independently by each source. It lists the conditions for applying superposition theorem as the circuit elements being linear and the sources being independent. It provides steps for using superposition theorem which involve solving the circuit for each source independently and then summing the contributions. An example problem demonstrates using superposition theorem to find the total current in a circuit. Finally, it discusses an application of superposition theorem in separating contributions of DC and AC sources.

1. Submitted By:
Imran Hossain Chowdhury
ID:191-141-002
EEE,44th Batch
Superposition Theorem

2. Overview
 Definition
 Conditions to Apply
 Steps to Apply
 Example
 Usage

3. Definition
Superposition Theorem states that voltage or
current through an element of a linear, bilateral
network having multiple sources is equivalent to
the summation of generated voltage or current
across that element, independently by each
source present in the network. While at the time
of considering a single source all other sources
are replaced by their respective internal
impedances.
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4. Conditions to Apply
1. SPT is applicable to both, AC and DC circuits.
2. The elements in the circuit can be resistors(DC),
capacitors or inductors(AC).
3. Semiconductor devices like diodes are usually
nonlinear, so cannot be applied SPT.
4. SPT works for current and voltage, but not
power.

5. Steps to Apply
1. Turn off all independent sources except one.
2. Redraw circuit.
3. Solve for the voltages and currents in the new
circuit.
4. Turn off the active independent source and turn
on one of the other independent sources.
5. Repeat Steps 2 and 3.
6. Continue until you have turned on each of the
independent sources in the original circuit.
7. To find the total voltage across each component
and the total current flowing, add the
contributions from each of the voltages and
currents found in Step 3.

6. Steps to Apply

7. Example
Find the current I using Superposition Theorem.
I

8. Example
Case-1: Only with Voltage Source
I1 = 20∠0/ (4 + j4)
= 20∠0 / (5.65∠45)
= 3.53∠- 45 or 2.49 –j2.49 A

9. Example
Case-2: Only with Current Source
I2 = 4∠90 × 4j/ (4 + j4)
= 4∠90 × 4∠90 (5.65∠45)
= 4∠90 × 0.707∠45
= 2.828∠135 or -1.99 + j1.99 A

10. Example
Resultant Current:
I = I1 + I2
= 3.53∠- 45 + 2.828∠135
= 0.785∠45 or 0.56 + j0.56 A

11. Usage
Separating the contributions of the DC and AC
independent sources.
Example: To determine the performance of
an amplifier, we calculate the DC voltages and
currents to establish the bias point. The AC signal
is usually what will be amplified. A generic
amplifier has a constant DC operating point, but
the AC signal’s amplitude and frequency will vary
depending on the application.