Post on 03-Apr-2018
7/28/2019 BJT Biasing (Complete)
1/64
1. Structure of the Lesson
Intro
Class
Class end
Study
Assessment
Review
1. intro Overview of the lesson2. Learning objective present learning objective of the lesson3. Table of Content structure of the topics and subtopics in thelesson
4. Lecture (75-90 minutes) present the lecture in detailed topics that covers all the
learning objectives of the lesson.- each topics should be divided into subtopics
(5-15 min in length is recommended)- if a subtopic goes over 15 minutes divide the subtopic into
series of subtopics.
7/28/2019 BJT Biasing (Complete)
2/64
Course Circuit theory and Laboratory
Lesson # Lesson 2
Title Bipolar Junction Transistor biasing
SME Dr. Nguyen Vu Thang
7/28/2019 BJT Biasing (Complete)
3/64
Intro
The basic of electronic system is semiconductor device. The most famous and commonly used
active devices are BJTs (Bipolar Junction Transistors) and FET (Field Effect Transistor).
BJT can be use as amplifier and logic switches.
Pre-required knowledge: structure and operation of diode
7/28/2019 BJT Biasing (Complete)
4/64
Learning Objectives Table of Content
At the end of this chapter, the students shoul
be able to:
Understand the basic transistor operation
& configuration
Discuss transistor parameters and
characteristics
Operating point
Bias circuit
Design Operations
Transistor switching network
PNP Transistors
Bias Stabilization
7/28/2019 BJT Biasing (Complete)
5/64
Operating Point
Operating point
within the limits of
operation of
transistor
IC (MA)
ICMAX
Saturation
5
10
15
20
25
IB = 0 A
10 A
20 A
30 A
40 A
50 A
60 A
70 A
80 A
A
B
C
D
VCE (V)VCESAT Cutoff
VCEMAX
5 10 15 20
PCmax
7/28/2019 BJT Biasing (Complete)
6/64
Bias Circuit
Fixed bias Circuit
Emitter stabilized bias Circuit
Voltage - divider bias Circuit DC Bias with Voltage Feedback
Miscellaneous bias configuration
7/28/2019 BJT Biasing (Complete)
7/64
Fixed-bias Circuit
Vcc
RB RC IC
IB
B
C
E
+
__+
VBE
C1
C2
RB
RC
IC
IB
B
C
E
+
+
VBE
__
Vcc Vcc
7/28/2019 BJT Biasing (Complete)
8/64
Fixed-bias Circuit
RB
Vcc IB
+
+
_
_VBE
Forward Bias of Base-Emitter
Base-Emitter loop
+ VccIBRB VBE= 0
=
Collector-Emitter loop
Collector-Emitter loop
+
IC
+
_
RC
Vcc
VCE
_
=
+ = 0
=
7/28/2019 BJT Biasing (Complete)
9/64
Fixed-bias Circuit
=
Load Line Analysis
Vcc
RC
RB
IC
IB
VCE
_
+
+
_
(V)
0
IC (MA)
IB = 0 A
10 A
20 A
30 A
40 A
50 A
VCE (V)5 10 15
7/28/2019 BJT Biasing (Complete)
10/64
Fixed-bias Circuit**
7/28/2019 BJT Biasing (Complete)
11/64
Fixed-bias Circuit
7/28/2019 BJT Biasing (Complete)
12/64
Fixed-bias Circuit
7/28/2019 BJT Biasing (Complete)
13/64
Emitter stabilized bias circuit
7/28/2019 BJT Biasing (Complete)
14/64
Emitter stabilized bias circuit
7/28/2019 BJT Biasing (Complete)
15/64
Emitter stabilized bias circuit
(V)
0
7/28/2019 BJT Biasing (Complete)
16/64
Emitter stabilized bias circuit
For the emitter bias network, determine:
7/28/2019 BJT Biasing (Complete)
17/64
Emitter stabilized bias circuit
7/28/2019 BJT Biasing (Complete)
18/64
Voltage -divider bias circuit
7/28/2019 BJT Biasing (Complete)
19/64
Voltage -divider bias circuit
7/28/2019 BJT Biasing (Complete)
20/64
Voltage -divider bias circuitDetermine the dc bias voltage and the current IC for the voltagedivider
configuration
7/28/2019 BJT Biasing (Complete)
21/64
Voltage -divider bias circuit
Solution
RTH = R1 R2 = 3.55k
ETH =2V
IB = 6.05 A
IC = IB= (140)(6.05 A)
=0.88mA
VCE = VCC IC ( RC + RE )
=22V( 0.85 mA )( 10 + 1.5)= 22v 9.8V
=12.22 V
7/28/2019 BJT Biasing (Complete)
22/64
DC Bias with Voltage Feedback
7/28/2019 BJT Biasing (Complete)
23/64
DC Bias with Voltage Feedback
7/28/2019 BJT Biasing (Complete)
24/64
DC Bias with Voltage Feedback
Determine the quiesent levels of ICQ and VCEQ
EXAMPLE
7/28/2019 BJT Biasing (Complete)
25/64
DC Bias with Voltage Feedback
7/28/2019 BJT Biasing (Complete)
26/64
DC Bias with Voltage Feedback
repeat above example using a beta of 135 ( 50 % more than above example )
7/28/2019 BJT Biasing (Complete)
27/64
DC Bias with Voltage Feedback
7/28/2019 BJT Biasing (Complete)
28/64
DC Bias with Voltage Feedback
Determine the dc level of IB and Vc
7/28/2019 BJT Biasing (Complete)
29/64
DC Bias with Voltage Feedback
7/28/2019 BJT Biasing (Complete)
30/64
Miscellaneous bias configuration
ExampleFor the network of fig
a)Determine ICQ and VCEQ
b)Find VB ,VC , VE and VBC
7/28/2019 BJT Biasing (Complete)
31/64
Miscellaneous bias configuration Solution
a)The absence ofREreduces the reflection of resistive levels to
simply that ofRCand the equation for IB reduces to
IB=;
= ;.
()(.)=
9.
.
=15.51 A
ICQ=IB =(120)(15.51 A)
= 1.86 mA
VCEQ =VCC- ICRC
= 20V(1.86Ma)(4.7k)
= 11.26VVB =VBE=0.7 V
VC =VCE=11.26 V
VE =0 V
VBC=VB VC=0.7 V - 11.26 V
=-10.56 V
7/28/2019 BJT Biasing (Complete)
32/64
Miscellaneous bias configuration
EXAMPLEDetermine VC and VB for the network of fig
7/28/2019 BJT Biasing (Complete)
33/64
Miscellaneous bias configuration
7/28/2019 BJT Biasing (Complete)
34/64
Miscellaneous bias configurationEXAMPLE
Determine VCEQand IE for the network of fig
7/28/2019 BJT Biasing (Complete)
35/64
Miscellaneous bias configurationSolution:
Applying Kirchhoffs voltage law to
the input circuit will result in
-IBRBVBEIERE+VEE= 0
But IE= (+1)IB
And VEE-VBE-(+1)IBRB-IBRB = 0
With IB=;
()
Substituting values yields
IB=;.
(9)()
=
9.
=
9.
= 45.73 A
IC= IB
= (90)(45.73A)
= 4.12 mA
Applying Kirchhoffs voltage law to the output
circuit, we have
-VEE + IERE+ VCE=0
But IE =(+1)IBAnd VCEQ = VEE(+1)IBRE
=20 V(91)(45.73 A)(2k)
=11.68 V
IE =4.16 mA
7/28/2019 BJT Biasing (Complete)
36/64
Miscellaneous bias configuration
EXAMPLE
Determine the voltage VCB and the current
IB for the commom-base configuration
7/28/2019 BJT Biasing (Complete)
37/64
Miscellaneous bias configurationSolution
Applying Kirchhorrs voltage law to the input circuit yields
-VEE+ IERE+ VBE= 0
And IE=;
Substituting values, we obtain
IE= ;.
. = 2.75 mA
Applying Kirchhoffs voltage law to the output circuit gives
-VCB + ICRCVCC= 0
And VCB = VCCICRCwith IC IE
=10 V(2.75 mA)(2.4k)
=3.4 V
IB =
=.
= 45.8 A
7/28/2019 BJT Biasing (Complete)
38/64
Design Operations
Design of a Bias Circuit with an Emitte Feedback Resistor
7/28/2019 BJT Biasing (Complete)
39/64
Design Operations
Determine the resistor values for the network for the indicated operating point and supplyvoltage
7/28/2019 BJT Biasing (Complete)
40/64
Design Operations
VE =
VCC =
= 2V
RE =
=
=
mA= 1k
RC =
=;CE;
=;;
mA = 4k
IB =
=
mA
= 13.33A
RB =
=
;BE;
=
;.;
.= 1.3M
7/28/2019 BJT Biasing (Complete)
41/64
Design OperationsDesign of Current-Gain-Stabilized (Beta-Independent) Circuit
7/28/2019 BJT Biasing (Complete)
42/64
Design Operations
RE
_
R1
R2
RC C2
CE
C1
VCC = 20V
100F
10F
10F = 8
= 10
AC input
AC output
+
Determine the levels of RC, RE, R1, and R2, for the network of this Figure for
the operating point indicated
7/28/2019 BJT Biasing (Complete)
43/64
Design Operations
RE
_
R1
R2
RC C2
CE
C1
VCC = 20V
100F
10F
10F
= 8
= 10AC
input
AC
output+
VE =
VCC =
= 2V
RE =
=
=
mA= 200
RC =
=
;CE;
=
;;
mA= 1k
VB = VBE + VE = 0.7 + 2 = 2.7V
7/28/2019 BJT Biasing (Complete)
44/64
Transistor switching network
RB
RC
VCC = 5V
68
0.82
= 125
Vi
5V
0V
VC
t
5V
0V
0 0
6.1
= 5
7/28/2019 BJT Biasing (Complete)
45/64
Transistor switching network
RB
RC
VCC = 5V
= 250
t
VC
10V
0V
10V
t
VC
10V
0V 0V
Example:Determine RB and RC for the transistor inverter of this Figure if ICsax = 10mA
7/28/2019 BJT Biasing (Complete)
46/64
Transistor switching networkAt saturation:
ICsat=
R
and 10mA =
R
so that RC=
mA= 1k
At saturation:
IB=
=
mA
= 40AChoosing IB = 60A to ensure saturation and using:
IB =i;.
R
We obtain:
RB=i;.
I=
;.
A= 155k
Choose RB= 150k, which is a standard value. Then
IB =i;.
R=
;.
k= 62A
And IB = 62A
= 40A
Therefore, use
RB= 150k, R
C= 1k
7/28/2019 BJT Biasing (Complete)
47/64
PNP Transistor
IC+
RC
_
+
_
+_
VCE
+
_
RE
_
IE
IB
-IERE +VBE - IBRB +VCC = 0
IB =CCBE
R()R
-IERE +VCE ICRC +VCC = 0
VCE = -VCC + IC(RE+RC)
7/28/2019 BJT Biasing (Complete)
48/64
PNP Transistor
CB
E
+VBE_
10F
10F47
2.4
1.1
10
Vi
18
Example: Determine VCE for the voltage-divider bias configuration of thisFigure
7/28/2019 BJT Biasing (Complete)
49/64
PNP TransistorTesting the condition: RE 10R2
Results in: (120)(1.1k) 10(10 k)
132 k 100 k (sastified)
Solving for VB, we have:
VB =RCC
R
R
= k (; )
k k= 3.16V
Note the similarity in format of the equation with the resulting negative voltage for
VB.
Applying Kirchhoffs voltage law around the base-emitter loop yields: VB - VBE VE = 0
and VE = VB VBE
Substituting values, we obtain
VE= -3.16 V (-0.7 V)
= -3.16 V + 0.7 V
= -2.46 V
7/28/2019 BJT Biasing (Complete)
50/64
PNP Transistor
7/28/2019 BJT Biasing (Complete)
51/64
Bias stabilization
: : 7.5 (
)
: 10
7/28/2019 BJT Biasing (Complete)
52/64
Bias stabilization
Shift in dc bias point due to change in temperature: 25 C and 100 C
7/28/2019 BJT Biasing (Complete)
53/64
Bias stabilization
=
=
=
=
+ ( + 1)
=
=( 1 + /)
( 1 + + /)
:
= ( + 1)1 + /
+ 1 + /
/ ( + 1): = + 1
= ( + 1) 1 + /
+ 1 + /
= ( + 1)1 + /
+ 1 + /
7/28/2019 BJT Biasing (Complete)
54/64
Bias stabilization
ExampleCalculate the stability factor and the change in IC from 25
oC to 100oC for the transistor
defined by the Table for the following emitter-bias arrangements.
(a) RB/RE = 250 ( RB = 250 RE)
(b) RB/RE = 10 ( RB = 10 RE)
(c) RB/RE = 0.01 ( RE = 100 RB)
7/28/2019 BJT Biasing (Complete)
55/64
Bias stabilization
7/28/2019 BJT Biasing (Complete)
56/64
Bias stabilizationDetermine the stability factor S(VBE) and the change in IC from 25
oC to 100oC for the transistor defined by the
Table for the following bias arrangements.
(a) Fixed-bias with RB= 240k and = 100.
(b) Emitter-bias with RB=240k, RE=1k, and =100.
(c) Emitter-bias with RB=47k, RE=4.7k, and =100.
7/28/2019 BJT Biasing (Complete)
57/64
Bias stabilization
7/28/2019 BJT Biasing (Complete)
58/64
Bias stabilization
Determine the stability factor S(VBE) and the change in IC from 25
o
C to 100
o
C for the transistor defined bythe Table for the following bias arrangements.(a) Fixed-bias with RB = 240k and = 100.(b) Emitter-bias with RB=240k, RE=1k, and =100.(c) Emitter-bias with RB=47k, RE=4.7k, and =100.
Assessment Quiz 1
7/28/2019 BJT Biasing (Complete)
59/64
Assessment Quiz 2
7/28/2019 BJT Biasing (Complete)
60/64
Assessment Quiz 3
7/28/2019 BJT Biasing (Complete)
61/64
Assessment Quiz 4
7/28/2019 BJT Biasing (Complete)
62/64
IB, IC, VC?
Assessment Quiz 5
7/28/2019 BJT Biasing (Complete)
63/64
Determine the following for the network of the above figure
(a) S(ICO)
(b) S(VBE
)
(c) S() using T1as the temperature at which the parameter values are specified at (T2) as 25% more than (T1).
(d) Determine the net change in IC if a change in operating conditions results in ICO increasing from 0.2 to 10A,
VBE drops from 0.7 to 0.5V, and increases 25%.
Review
7/28/2019 BJT Biasing (Complete)
64/64
Summary: this chapter provide Operating point, Bias circuits, Transistor switching network,
Bias Stabilization.
Main Bias circuits are: Fixed bias Circuit , Emitter stabilized bias Circuit,
Voltage - divider bias Circuit