Voltage divider bias circuit and its analysis is discussed

1. Voltage divider bias circuit
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2. Problem #1
Assume that a Si transistor with β=200, VBE=0.7V, VCC=15V
and R1=34KΩ , R2=5.9KΩ , Rc=1KΩ , RE=510Ω is used in voltage
divider bias circuit. Find the bias point.
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3. Problem #2
Assume that a Si transistor with β=100 and VBE=0.7V is used in
voltage divider bias circuit as shown below.
Find the bias point
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4. Problem #3
Assume that a Si transistor with β=50, VBE=0.6V, VCC=22.5V
and RC=5.6KΩ is used in voltage divider bias circuit. It is
desired to establish a Q-point at VCE=12V, IC=1.5mA and a
stability factor of S≤3. Find RE,R1,R2
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5. Problem #3 Solution
Step 1: Find RE
Apply KVL around CE loop
E
C
CECCCC R
I
VRIV







1
EECECCCC RIVRIV 
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6. Problem #3 Solution
Step 2: Find RTH and VTH
  
  BE
BE
BE
E RR
RR
RR
R
S











1
1
1
1
EEBETHBTH RIVRIV 
E
C
BETH
C
TH R
I
VR
I
V


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7. Problem #3 Solution
Step 3: Find R1 and R2
21
2
RR
RV
V CC
TH


21 || RRRTH 
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8. Problem #4
Assume that a Si transistor with β=50, VBE=0.6V, VCC=10V and
RC=3.5KΩ is used in voltage divider bias circuit. It is desired to
establish a Q-point at VCE=5V, IC=1mA and a stability factor of
S≤10. Show the circuit diagram with all the components
values.
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9. Problem #5
Assume that a Si transistor with β=99, VBE=0.6V, VCC=12V and
RC=2.2KΩ is used in voltage divider bias circuit. It is desired to
establish a Q-point at VCE=5V, IC=2mA and a stability factor of
S≤10. Show the circuit diagram with all the components
values.
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10. VB
Problem #6
Assume that a Si transistor with β=100 and
VBE=0.7V Determine the bias point
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11. VB
Problem #6 solution
12
2
RR
R
VV CCB


12
21
RR
RR
RB


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12. Problem #6 solution
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13. Problem #6 solution
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14. Problem #7
Assume that a Si transistor with β=200 and
VBE=0.7V Determine the bias point
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15. Problem #7
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16. Problem #7
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17. Problem #8
Assume that a Si transistor with β=∞, VBE=0.7V, and VCC=3V is
used in voltage divider bias circuit shown below. Determine
the required value of R2(in KΩ) to produce IC=1mA.
VB
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18. Problem #8 Solution
Given β=∞
IC=IE ( since IB=0)
VB
12
2
RR
R
VV CCB


EBEB VVV 
EEE RIV 
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