Voltage Divider Bias ELEC 121. January 2004ELEC 1212 BJT Biasing 3 For the Voltage Divider Bias...
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Transcript of Voltage Divider Bias ELEC 121. January 2004ELEC 1212 BJT Biasing 3 For the Voltage Divider Bias...
![Page 1: Voltage Divider Bias ELEC 121. January 2004ELEC 1212 BJT Biasing 3 For the Voltage Divider Bias Configurations Draw Equivalent Input circuit Draw Equivalent.](https://reader037.fdocuments.us/reader037/viewer/2022110210/56649eb55503460f94bbe5a6/html5/thumbnails/1.jpg)
Voltage Divider Bias
ELEC 121
![Page 2: Voltage Divider Bias ELEC 121. January 2004ELEC 1212 BJT Biasing 3 For the Voltage Divider Bias Configurations Draw Equivalent Input circuit Draw Equivalent.](https://reader037.fdocuments.us/reader037/viewer/2022110210/56649eb55503460f94bbe5a6/html5/thumbnails/2.jpg)
January 2004 ELEC 121 2
BJT Biasing 3For the Voltage Divider Bias Configurations• Draw Equivalent Input circuit• Draw Equivalent Output circuit• Write necessary KVL and KCL Equations• Determine the Quiescent Operating Point
– Graphical Solution using Loadlines– Computational Analysis
• Design and test design using a computer simulation
![Page 3: Voltage Divider Bias ELEC 121. January 2004ELEC 1212 BJT Biasing 3 For the Voltage Divider Bias Configurations Draw Equivalent Input circuit Draw Equivalent.](https://reader037.fdocuments.us/reader037/viewer/2022110210/56649eb55503460f94bbe5a6/html5/thumbnails/3.jpg)
January 2004 ELEC 121 3
Voltage-divider bias configuration
![Page 4: Voltage Divider Bias ELEC 121. January 2004ELEC 1212 BJT Biasing 3 For the Voltage Divider Bias Configurations Draw Equivalent Input circuit Draw Equivalent.](https://reader037.fdocuments.us/reader037/viewer/2022110210/56649eb55503460f94bbe5a6/html5/thumbnails/4.jpg)
January 2004 ELEC 121 4
Voltage Divider Input Circuit Approximate AnalysisThe Approximate method may be used only when R2 .1 RE
Under these conditions RE does not significantly load R2 and it is effect may be ignored: IB << I1 and I2 and I1 I2 Therefore:
We may apply KVL to the input, which gives us:
-VB + VBE + IE RE = 0
Solving for IE we obtain:
2B CC
1 2
RV = V
R + R
B BE
EE
V - V I =
R
![Page 5: Voltage Divider Bias ELEC 121. January 2004ELEC 1212 BJT Biasing 3 For the Voltage Divider Bias Configurations Draw Equivalent Input circuit Draw Equivalent.](https://reader037.fdocuments.us/reader037/viewer/2022110210/56649eb55503460f94bbe5a6/html5/thumbnails/5.jpg)
January 2004 ELEC 121 5
Input Circuit Exact AnalysisThe Exact Analysis method is always valid must be used when R2 > .1 RE
Perform Thevenin’s Theorem using the transistor as the loadOpen the base lead of the transistor, and the Voltage Divider bias circuit is:
Calculate RTH
2TH CC
1 2
RV = V
R + R
We may apply KVL to the input, which gives us:-VTH + IB RTH + VBE + IE RE = 0Since IE = ( + 1) IB
ESolving for I we obtain:
THTH E BE E E
TH BEE
THE
R-V + I + V + I R = 0
β + 1
V - V I =
R + R
β + 1
![Page 6: Voltage Divider Bias ELEC 121. January 2004ELEC 1212 BJT Biasing 3 For the Voltage Divider Bias Configurations Draw Equivalent Input circuit Draw Equivalent.](https://reader037.fdocuments.us/reader037/viewer/2022110210/56649eb55503460f94bbe5a6/html5/thumbnails/6.jpg)
January 2004 ELEC 121 6
Redrawing the input circuit for the network
![Page 7: Voltage Divider Bias ELEC 121. January 2004ELEC 1212 BJT Biasing 3 For the Voltage Divider Bias Configurations Draw Equivalent Input circuit Draw Equivalent.](https://reader037.fdocuments.us/reader037/viewer/2022110210/56649eb55503460f94bbe5a6/html5/thumbnails/7.jpg)
January 2004 ELEC 121 7
Determining VTH
2TH CC
1 2
RV = V
R + R
![Page 8: Voltage Divider Bias ELEC 121. January 2004ELEC 1212 BJT Biasing 3 For the Voltage Divider Bias Configurations Draw Equivalent Input circuit Draw Equivalent.](https://reader037.fdocuments.us/reader037/viewer/2022110210/56649eb55503460f94bbe5a6/html5/thumbnails/8.jpg)
January 2004 ELEC 121 8
Determining RTH
1 2TH
1 2
R R R =
R + R
![Page 9: Voltage Divider Bias ELEC 121. January 2004ELEC 1212 BJT Biasing 3 For the Voltage Divider Bias Configurations Draw Equivalent Input circuit Draw Equivalent.](https://reader037.fdocuments.us/reader037/viewer/2022110210/56649eb55503460f94bbe5a6/html5/thumbnails/9.jpg)
January 2004 ELEC 121 9
The Thévenin Equivalent Circuit
Note that VE = VB – VBE and IE = ( + 1)IB
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January 2004 ELEC 121 10
Input Circuit Exact Analysis
We may apply KVL to the input, which gives us:-VTH + IB RTH + VBE + IE RE = 0Since IE = ( + 1) IB
ESolving for I we obtain:
THTH E BE E E
TH BEE
THE
R-V + I + V + I R = 0
β + 1
V - V I =
R + R
β + 1
![Page 11: Voltage Divider Bias ELEC 121. January 2004ELEC 1212 BJT Biasing 3 For the Voltage Divider Bias Configurations Draw Equivalent Input circuit Draw Equivalent.](https://reader037.fdocuments.us/reader037/viewer/2022110210/56649eb55503460f94bbe5a6/html5/thumbnails/11.jpg)
January 2004 ELEC 121 11
Collector-Emitter Loop
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January 2004 ELEC 121 12
Collector-Emitter (Output) Loop
Applying Kirchoff’s voltage law: - VCC + IC RC + VCE + IE RE = 0
Assuming that IE IC and solving for VCE: IC = VCC – VCE – (RE + RC)
Solve for VE: VE = IE RE
Solve for VC: VC = VCC - IC RC
or
VC = VCE + IE RE
Solve for VB: VB = VCC - IB RB or
VB = VBE + IE RE
![Page 13: Voltage Divider Bias ELEC 121. January 2004ELEC 1212 BJT Biasing 3 For the Voltage Divider Bias Configurations Draw Equivalent Input circuit Draw Equivalent.](https://reader037.fdocuments.us/reader037/viewer/2022110210/56649eb55503460f94bbe5a6/html5/thumbnails/13.jpg)
January 2004 ELEC 121 13
Voltage Divider Bias Example 1
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January 2004 ELEC 121 14
Voltage Divider Bias Example 2
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January 2004 ELEC 121 15
Design of CE Amplifier with Voltage Divider Bias
1. Select a value for VCC
2. Determine the value of from spec sheet or family of curves3. Select a value for ICQ
4. Let VCE = ½ VCC (typical operation, 0.4 VCC ≤ VC ≤ 0.6 VCC )
5. Let VE = 0.1 VCC (for good operation, 0.1 VCC ≤ VE ≤ 0.2 VCC )6. Calculate RE and RC
7. Let R2 ≤ 0.1 RE (for this calculation, use low value for )8. Calculate R1
CC B1 2
B
V - V R = R
V
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January 2004 ELEC 121 16
CE Amplifier Design• Design a Common Emitter Amplifier with Voltage Divider
Bias for the following parameters:
VCC = 24V
IC = 5mAVE = .1VCC
VC = .55VCC
= 135
![Page 17: Voltage Divider Bias ELEC 121. January 2004ELEC 1212 BJT Biasing 3 For the Voltage Divider Bias Configurations Draw Equivalent Input circuit Draw Equivalent.](https://reader037.fdocuments.us/reader037/viewer/2022110210/56649eb55503460f94bbe5a6/html5/thumbnails/17.jpg)
January 2004 ELEC 121 17
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January 2004 ELEC 121 18
CE Amplifier Design
![Page 19: Voltage Divider Bias ELEC 121. January 2004ELEC 1212 BJT Biasing 3 For the Voltage Divider Bias Configurations Draw Equivalent Input circuit Draw Equivalent.](https://reader037.fdocuments.us/reader037/viewer/2022110210/56649eb55503460f94bbe5a6/html5/thumbnails/19.jpg)
January 2004 ELEC 121 19
CE Amplifier Design Voltage Divider Bias
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January 2004 ELEC 121 20
Voltage Divider Bias with Dual Power Supply
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January 2004 ELEC 121 21
Voltage Divider Bias with Dual Power Supply
Input Circuit Find VTH and RTH
2 1TH CC EE
1 2
2TH1 CC
1 2
EE
1TH2 EE
1 2
TH TH
1 2
1 2TH
1 2
1 TH2
R V = V
R + R
(Note V is negative)
R V = V
R + R
V =
R R V = V - V
R + R R + R
R R R =
R +
V - V
R
![Page 22: Voltage Divider Bias ELEC 121. January 2004ELEC 1212 BJT Biasing 3 For the Voltage Divider Bias Configurations Draw Equivalent Input circuit Draw Equivalent.](https://reader037.fdocuments.us/reader037/viewer/2022110210/56649eb55503460f94bbe5a6/html5/thumbnails/22.jpg)
January 2004 ELEC 121 22
Voltage Divider Bias with Dual Power Supply
Output Circuit
CC
CC C C CE E E EE
E C
C E
EE CEC
C E
CC EE CEC
C E
V + V - V I =
R +
-V + I R + V + I R - V = 0
If we assume I @ I (β > 100)
If R
V + V -
we use
V I =
I =
R +
I
αR
α
![Page 23: Voltage Divider Bias ELEC 121. January 2004ELEC 1212 BJT Biasing 3 For the Voltage Divider Bias Configurations Draw Equivalent Input circuit Draw Equivalent.](https://reader037.fdocuments.us/reader037/viewer/2022110210/56649eb55503460f94bbe5a6/html5/thumbnails/23.jpg)
January 2004 ELEC 121 23
Voltage Divider Bias with Dual Power Supply
![Page 24: Voltage Divider Bias ELEC 121. January 2004ELEC 1212 BJT Biasing 3 For the Voltage Divider Bias Configurations Draw Equivalent Input circuit Draw Equivalent.](https://reader037.fdocuments.us/reader037/viewer/2022110210/56649eb55503460f94bbe5a6/html5/thumbnails/24.jpg)
PSpice Simulation
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January 2004 ELEC 121 25
PSpice Bias Point Simulation
![Page 26: Voltage Divider Bias ELEC 121. January 2004ELEC 1212 BJT Biasing 3 For the Voltage Divider Bias Configurations Draw Equivalent Input circuit Draw Equivalent.](https://reader037.fdocuments.us/reader037/viewer/2022110210/56649eb55503460f94bbe5a6/html5/thumbnails/26.jpg)
January 2004 ELEC 121 26
PSpice Simulation for DC Bias
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January 2004 ELEC 121 27
PSpice Simulation for DC Sweep
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January 2004 ELEC 121 28
PSpice Simulation for DC Sweep
The response of VCE demonstrates that it reaches a peak value near the Q point and then decreases
The response of VC demonstrates rises rapidly towards the Q Point and then increases gradually towards a maximum value
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January 2004 ELEC 121 29
Simulation Settings for AC Sweep
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January 2004 ELEC 121 30
Probe Output for AC Sweep