36.voltage divider bias

1. BJT
Voltage Divider Biasing
1

2. Objectives
At the end of the module the student would be
able to explain
Study Voltage Divider Bias
2

3. Voltage Divider Bias Circuit
Provides good Q-point stability
with a single polarity supply
voltage
1
st
step: Locate capacitors and
replace them with an open circuit
2
nd
step: Simplified circuit using
Thevenin Theorem
3
rd
step: Locate 2 main loops
which;
BE loop
CE loop
3

4. Voltage Divider Bias Circuit
1
st
step: Locate capacitors and replace them with
an open circuit
4

5. Voltage Divider Bias Circuit
■2
nd
step: : Simplified circuit using Thevenin
Theorem
5
Thevenin Theorem; 21
21
21//
RR
RR
RRR
TH
+
´
==
CCTH V
RR
R
V
21
2
+
=
From Thevenin Theorem;

6. Voltage Divider Bias Circuit
■3
rd
step: : Locate 2 main loops.
6
2
BE Loop CE Loop
1
2

7. Voltage Divider Bias Circuit
BE Loop Analysis
7
1
Recall;
Substitute for IE
0=---
EEBETHBTH RIVRIV
ERTH
BETH
B
EBBETHBTH
RR
VV
I
RIVRIV
)1(
0)1(
++
-
=\
=+---
b
b
BE II )1(+=b

8. Voltage Divider Bias Circuit
CE Loop Analysis
8
2
Assume;
Therefore;
CE
II»
0=---
EECECCCC RIVRIV
)(
ECCCCCE RRIVV +-=\

9. Build the circuit as shown below and find out
the following parameters I
C , I
B , V
B, V
E and V
C
Voltage Divider Bias Circuit
9

10. Voltage Divider Bias Circuit
10

11. Simulation and Results
Run DC analysis with Default Settings
Observe the output on voltmeters and
ammeters
11

12. Access it Online
12
You can access this experiment from the link below
http://www.docircuits.com/public-circuit/380/bjt-voltage-divider-bias