DAR ES SALAAM INSTITUTE OF TECHNOLOGY
Department of: Computer Studies
Assignment:3
Module Code: ETU 07321
Module Name: ANALOGUE ELECTRONICS
Class: Beng21 COE 1
GROUP 1
S\N
Names
Registration Number
1
SALEH KHAMIS MOHAMED
2102302216520
2
KABIR ALI ABEID
2102302217601
3
NATASHA HALIM LOZZY
2102302117561
4
BARKE SALEH LAABDI
2102302117660
5
NASRI MOHAMED SIMBA
2102302216413
Remarks
THEVENIN’S THEOREM
State that “A liner two-terminal circuit can be replaced by an equivalent circuit consisting of a
voltage source VTH in series with a resistor RTH, where VTH is the open circuit voltage at the
terminal and RTH is input or equivalent resistance at the terminal when the independent sources
are turned off”.
Steps for applying Thevenin’s Theorem
1. Open the two terminal (remove any load) between which you want to find Thevenin’s
equivalent circuit.
2. Determine the voltage (VTH) across the two open terminals
3. Determine the (RTH) between the two terminals with all voltage sources terminals with all
voltage sources shorted and all current sources opened
4. Connect VTH and RTH in series to produce the complete, Thevenin’s equivalent for the original
circuit
5. Place the load resistor removed in step 1 across the terminals of the Thevenin’s equivalent
circuit
Examples:
1. Calculate the Thevenin’s Voltage (VTH) and Resistance (RTH).
Solution:
Since 12Ω and 8Ω are in series (12Ω + 8Ω) = 20Ω
Therefore 20Ω is in parallel in 20Ω
R = (20 x 20 / 20 + 20) Ω
R = 10 Ω
Therefore;
Vs = (10 / 10+10) 100
Vs = 50 V
Therefore Voltage across 10Ω is 50Ω
Then:
VTH = (8 / 12+8) 50
VTH = 20V
Again;
R = (20 x 10 / 10 + 20)
R = (200 / 30)
R = 6.67Ω
Then
R = 6.67Ω + 12Ω = 18.67Ω
RTH = (18.67 x 8 / 18.67 + 8)
RTH = 5.6 Ω
2. Calculate, RTH , VTH and Thevenin’s Equivalent Circuit.
Solution:
VTH = (1 / 1+1) 20
VTH = 10V
Again:
RTH = (1x1 / 1+1) = (1 / 2 + 1) = 1.5 Ω
RTH = 1.5 Ω
Therefore;
Equivalent Thevenin’s circuit:
3.Find the Thevenin’s Equivalent Circuit between Output terminal A and B.
Solution:
Since no voltage drop across R4 , VAB equals R2 + R3 and VTH = VAB
Therefore we use voltage divider theorem ton find VTH
VTH = (R2 + R3 / R1 + R2 + R3) VS
VTH = (470 + 220 / 1 + 470 +220) x 10
VTH = (690 / 1690) x 10
VTH = 4.083V
Therefore to find RTH, R1 appears parallel with R2 + R3 and R4 is in series with parallel
combination of R1 , R2 and R3
RTH = (R1 (R2 +R3) / R1 + R2 +R3 ) + R4
RTH = (1(690) / 1.69 ) + 1
RTH = 1.41 KΩ