Title: INC 111 Basic Circuit Analysis
1INC 111 Basic Circuit Analysis
2Special Techniques
- Superposition Theorem
- Thevenins Theorem
- Nortons Theorem
- Source Transformation
3Linearity Characteristic
If RL change its value , how will it effect the
current and voltage across it?
4I
Voc Voltage open-circuit Isc Current
short-circuit
ISC
V
VOC
For any circuit constructed from only linear
components Not just RL, all resistors have
this property.
5Thevenins Theorem
When we are interested in current and voltage
across RL, we can simplify other parts in the
circuit.
Equivalent circuit
6I
ISC
Slope 1/R
V
VOC
Voc Voltage open-circuit Isc Current
short-circuit R R equivalent
7Thevenins Equivalent Circuit
Thevenins equivalent circuit
VTH Voc (by removing RL and find the voltage
difference between 2 pins) RTH (by looking into
the opened connections that we remove RL, see how
much resistance from the connections. If we see a
voltage source, we short circuit. If we see a
current source, we open circuit.)
8Why do we needequivalent circuit?
- To analyze a circuit with several values of RL
- For circuit simplification (source
transformation) - To find RL that gives maximum power (maximum
power transfer theorem)
9Procedure
- Remove RL from the circuit
- Find voltage difference of the 2 opened
connections. Let it equal VTH. - From step 2 find RTH by
- 3.1 short-circuit voltage sources
- 3.2 open-circuit current sources
- 3.3 Look into the 2 opened connections. Find
equivalent resistance.
10Example
Find Thevenins equivalent circuit and find the
current that passes through RL when RL 1?
11Find VTH
12Find RTH
Short voltage source
RTH
13Thevenins equivalent circuit
If RL 1?, the current is
14Example
Find Thevenins equivalent circuit
15Find VTH
16Find RTH
Open circuit current source
RTH
17Thevenins equivalent circuit
18Example Bridge circuit
Find Thevenins equivalent circuit
1910V
Find VTH
8V
2V
0V
VTH 8-2 6V
20Find RTH
RTH
21(No Transcript)
22Thevenins equivalent circuit
23Special Techniques
- Superposition Theorem
- Thevenins Theorem
- Nortons Theorem
- Source Transformation
24I
ISC
V
VOC
For any point in linear circuit
25Thevenins Equivalent Circuit
26Nortons Equivalent Circuit
In Isc from replacing RL with an electric wire
(resistance 0) and find the current Rn RTH
(by looking into the opened connections that we
remove RL, see how much resistance from the
connections. If we see a voltage source, we short
circuit. If we see a current source, we open
circuit.)
27Example
Find Nortons equivalent circuit and find the
current that passes through RL when RL 1?
28Find In
29Find Rn
Short voltage source
RTH
30Nortons equivalent circuit
If RL 1?, the current is
31Relationship BetweenThevenins and Nortons
Circuit
I
ISC
Slope - 1/Rth
V
VOC
32Nortons equivalent circuit
Thevenins equivalent circuit
Same R value
33Example
Find Nortons equivalent circuit
34Find In
35Find RTH
Open circuit current source
RTH
36Nortons equivalent circuit
37Thevenins equivalent circuit
Nortons equivalent circuit
0.2 x 15 3
38Equivalent Circuits withDependent Sources
We cannot find Rth in circuits with dependent
sources using the total resistance method.
But we can use
39Example
Find Thevenin and Nortons equivalent circuit
40Find Voc
41Solve equations I1 3.697mA I2 3.678mA
42Find Isc
43Find Isc
I1 0.632mA I2 0.421mA I3 -1.052 A Isc I3
-1.052 A
44Nortons equivalent circuit
Thevenins equivalent circuit