All course of transistor will cover for diploma

1. TRANSISTOR
EC&C SUBJECT
PREPARED BY : D.H.SHUKLA

2. WHY WE NEED ELECTRONICS
• Electronics is widely used in information
processing, telecommunication, and signal processing. The ability of
electronic devices to act as switches makes digital information-
processing possible.
• Commonly, electronic devices contain circuitry consisting primarily or
exclusively of active semiconductors supplemented with passive
elements; such a circuit is described as an electronic circuit.

4. ENERGY BAND

6. TYPES OF SEMICONDUCTOR

16. WHAT IS A TRANSISTOR?
• Semiconductors: ability to change
from conductor to insulator
• Can either allow current or prohibit
current to flow
• Useful as a switch, but also as an
amplifier
• Essential part of many
technological advances

17. A BRIEF HISTORY
• Guglielmo Marconi invents radio in 1895
• Problem: For long distance travel, signal must be amplified
• Lee De Forest improves on Fleming’s original vacuum tube to amplify
signals
• Made use of third electrode
• Too bulky for most applications

18. THE TRANSISTOR IS BORN
• Bell Labs (1947): Bardeen,
Brattain, and Shockley
• Originally made of
germanium
• Current transistors made of
doped silicon

19. http://www.computerhistory.org/semiconductor/timeline.html#1940s

21. • Construction
• two polarities:
npn and pnp

24. RECALL P-N JUNCTION
P N
W
Vappl > 0
-+
N P
W
Vappl < 0
-+
Forward bias, + on P, - on N
(Shrink W, Vbi)
Allow holes to jump over barrier
into N region as minority carriers
Reverse bias, + on N, - on P
(Expand W, Vbi)
Remove holes and electrons away
from depletion region
I
V
I
V

26. • Transistor action

29. TRANSISTOR CONFIGURATION

32. TRANSISTOR CHARACTERISTICS
• Common Base : Input & Output Characteristics

34. COMMON EMITTER

36. COMMON COLLECTOR

38. CONCLUSION
CB CE CC
Input Resistance Very low Medium High
Output Resistance Very high Medium Low
Current Gain Less then 1 More then 1 More then 1
Power gain Lower then CE High Higher then CB

39. QUESTIONS
• Explain working of NPN transistor
• Draw the input and output characteristics of common emitter (CE)
configuration.
• Compare three configurations of transistor.

42. DC CURRENT GAIN
• 𝛼 𝑑𝑐 =
𝐼𝑐
𝐼𝐸
(Ratio of Collector Current to Emitter
Current)
• 𝑑𝑐 =
𝐼𝑐
𝐼𝐵
(Ratio of Collector Current to Base Current)
• 𝛼 𝑑𝑐= hFB
• 𝑑𝑐 = hFB

43. AC CURRENT GAIN (WHEN USE AS
AMPLIFIER)
• 𝛼 𝑎𝑐 =
𝐼𝑐
𝐼𝐸
(𝑊ℎ𝑒𝑛 𝑉𝐶𝐵 𝐶𝑜𝑛𝑠𝑡𝑎𝑛𝑡)
• 𝑎𝑐 =
𝐼𝑐
𝐼𝐵
(When VCE Constant)

44. RELATION BETWEEN 𝛼 𝑑𝑐 &  𝑑𝑐

45. CONTINUE…
• 𝛽𝑑𝑐 =
𝛼 𝑑𝑐
1−𝛼 𝑑𝑐
• 𝛼 𝑑𝑐 =
𝛽𝑑𝑐
1+𝛽𝑑𝑐

46. 𝑅𝑒𝑙𝑎𝑡𝑖𝑜𝑛 𝑏𝑒𝑡𝑤𝑒𝑒𝑛 𝛼 𝑎𝑐 AND  𝑎𝑐
• IE = IC + IB
• 𝐼𝐸 = 𝐼C + 𝐼𝐵 (FOR AC)
• DIVIDED BY 𝐼𝑐
• 𝐼𝐸
𝐼𝐶
= 1 +
𝐼𝐵
𝐼𝐶
• 1
𝛼
= 1+
1
𝛽
• 𝛽𝑑𝑐 =
𝛼 𝑑𝑐
1−𝛼 𝑑𝑐
• 𝛼 𝑑𝑐 =
𝛽𝑑𝑐
1+𝛽𝑑𝑐

50. QUESTION
• Define  and derive relation between two

51. AMPLIFIER

52. DIFFERENT AMPLIFIER IN MARKET

54. CE AMPLIFIER

56. WORKING

57. SOME PARAMETERS
• Voltage gain Av = Amplitude of output voltage ÷ Amplitude of
input voltage.
• Current gain Ai = Amplitude of output current ÷ Amplitude of input current.
• Power gain Ap = Signal power out ÷ Signal power in.

58. • Explain how transistor acts as an amplifier.
• Define amplifier. Explain common emitter amplifier.

59. TRANSISTOR BIASING
• What is Transistor biasing
• Transistor biasing is the process of setting a transistors DC operating
voltage or current conditions to the correct level so that any AC input
signal can be amplified correctly by the transistor.

60. NEED OF TRANSISTOR BIASING
1. To make a operating point at a centre of active region so for that
transistor will not go in saturation region
2. Operating point will not change with respect to temperature
3. If we change a transistor but parameters of transistor will not be
change

61. METHOD OF BIASING
• We can give a VBB,Vcc, VEE using only one battery
Here are a methods
1. Fixed biasing
2. Collector to Base Biasing
3. Emitter resistor Biasing
4. Voltage divider biasing

62. FIXED BIASING
• Here RB> RC then IC
>IB
• If Vcc and RB is fixed
so “Base current IB is
fixed that’s why is
biasing is called fixed
biasing “

63. ADVANTAGE & DISADVANTAGE
• Advantages: -
1. Circuit is simple
2. Less component Require
3. Resistor will not connect
between base to emitter so
input resistance will not goes
down so circuit will not load to
source
• Disadvantages: -
1. If temperature is increased then
ICBO and ICEO increased then IC
increased so temperature is also
increased
2. If we change a transistor then all
parameters are change and
operating points also change

64. COLLECTOR TO BASE (COLLECTOR
FEEDBACK BIAS)
• Here IB is depending upon
IC
• So if we increased a Ic then
IB is also increased
• Now to reduce a Ic then Rc
is increased consequences
voltage drop across Rc
increased so VcB
decreases
• That’s why if temperature is
goes up but stability is

65. ADVANTAGE & DISADVANTAGE
• Advantages: -
1. Circuit is simple
2. Less component Require
3. Stability factor is good
• Disadvantages: -
1. If temperature is increased then
little bit of operating point
decreased
2. Here RB is connected between
collector and base so feedback
is given by it. So negative
feedback is there so gain is
reduced

66. EMITTER RESISTOR BIAS(EMITTER
FEEDBACK BIAS)
• Here a one Resistor is connected with
emitter
• Suppose if temperature is increased then
collector current Ic is increased then so
voltage drop across Rc and RB increased
• This drop opposite to base current so base
current is reduce and so collector current
also reduce
• That’s why no change in operating point
and amplification factor 

67. ADVANTAGE & DISADVANTAGE
• Advantages: -
1. No change in operating point
and  if temperature is
increased
• Disadvantages: -
1. Feedback is negative so gain is
reduces
2. Costly circuit
Note:- To increase a gain then connect a capacitor across a base
resistor
A value of capacitor is 10 times base resistor value

68. VOLTAGE DIVIDER BIASING
• Here R1 and R2 are Biasing
resistor so Vb is fixed
• In this biasing operating point will
constant with respect to
temperature
• 𝐼1 = 𝐼2 + 𝐼𝐵 If we reduces a IB then
I1 = I2 so base potential is fixed
• VE = VB – VBE
• So IE = VE/RE
• Also IB is small then IC = IE
• And VCE = VCC – IC(RC – RE)

69. ADVANTAGE & DISADVANTAGE
• Advantages: -
1. No change in operating point
and  if temperature is
increased
2. Q point value is stable
• Disadvantages: -
1. Costly because required more
component
2. Stability factor is high therefore
chance to thermal runaway

70. QUESTIONS
• State the various biasing methods for transistor and explain any one
• Explain working of Voltage dividertype biasing with it circuit diagram

71. CASCADING AMPLIFIER
• When we want to a huge value of amplification then we make a
cascade connection between more then two amplifier,
• An Input of A2 is depending upon output of A1,
A1 A2 A3
Input Output

72. GAIN OF CASCADE AMPLIFIER
• Suppose gain of A1= Av1, A2 = Av2, A3 = Av3
• Total gain is Av = Av1 x Av2 x Av3 , If Av1 = 30, Av2 = 60, Av3 = 70
• Total = 30 x 60 x 70 = 1,26000
• Suppose this gain is defined in dB ( Decibel ) then
• AdB = AdB1 + AdB2 + AdB3 AdB = 20 log10 AV

73. LIMITATION OF CASCADE AMPLIFIER
•High cost
•Decrease a Bandwidth because lower cut-off frequency
increases and higher cut-off frequency is decreases
•It load a next stage

74. REQUIREMENTS FOR CASCADE
•One dc bias stage cannot effect an other dc bias
stage
•No any signal loss in coupling if it do then gain will
be reduce

75. METHODS TO CASCADE
•Direct Coupled
•RC Coupled
•LC Coupled
•Transformer Couple

76. DIRECT COUPLING

77. CONTINUE….
• In this method a two amplifier connected with simple wires
• An output signal is produce at collector of amplifier1 that directly gives
to base to another amplifier
• When input signal value is small and need to small amplification then
this method is helpful

78. ADVANTAGES & DISADVANTAGES
• Advantage
• 1. size is small
2. Low cost
3.Easy to design
• Dis-Advantages
• 1. 1st amplifier bias is affect a 2nd amplifier so need to separate VCC supply
• 2. Effect of temperature at output
• Application :- Thermocouple

79. RC COUPLED AMPLIFIER

80. CONTINUE…
Advantages
1. Less space required
2. Less cost
3. Use for medium Frequency
Disadvantages
1. Coupling Capacitor signal
Loss
2. For low signal amplification
need
 Application :-
Radio, T.V.,etc.

81. LC COUPLED

82. CONTINUE….
Advantages
1. Small dc voltage drop occurs so totally Vcc voltage utilised in
transistor
2. If impedance of choke is more then signal gain will be more
Disadvantages :-
1. Required More Space
2. Choke reactance will change with respect to frequency so response
is not same

83. TRANSFORMER COUPLING

84. CONTINUE…
Advantages
1. Low dc Voltage drop
2. Here Transformer in place of Rc so low power loss
3. No coupling capacitor so no loss in signal
4. Impedance matching can be done
Disadvantages :
1. Weight and size is more
2. Costly
3. Frequency response not clear

85. COMPARISON OF CASCADE AMPLIFIER
Parameters Direct Coupling RC Coupling LC
Coupling
Transformer
Coupling
Required
Space
Less then RC
Coupling
Less More More
Weight Lesser Less More More
Frequency
Response
Good Better Constant AF
Range
Not good
Impedance
Matching
Good Not good Poor Good
Cost Lesser Less More More
Application Amplify a Low
value of Signal
Voltage
Amplifier
Not use Power amplifier
and Tunde
Amplifier

86. QUESTION
• Explain necessity of cascading of amplifier.
• Compare a different types of cascade Amplifier

87. POWER AMPLIFIER
Power Amplifier
Signal With
Less Power
Signal With
More
Power

88. WHAT IS POWER AMPLIFIER
• An audio power amplifier (or power amp) is an electronic
amplifier that amplifies low-power electronic audio signals such
as the signal from radio receiver or electric guitar pickup to a
level that is high enough for driving loudspeakers or headphones

89. COMPARISON BETWEEN VOLTAGE & POWER
AMPLIFIER
Voltage Amplifier Power Amplifier
In voltage amplifier the amplitude of input
A.C signal is small.
In power amplifier the amplitude of input A.C
signal is large.
In voltage amplifier the collector current is
low, about 1 mA.
In power amplifier the collector current is
very high above greater than 100mA.
The transistor used can dissipate less heat
produced during its operation.
The transistor used can dissipate more heat
produced as compared to voltage amplifier
during its operation.
RC coupling is used in voltage amplifier.
In power amplifier invariably transformer
coupling is used.
The transistor used has thin base to handle
low current.
The transistor used has thick base to handle
large current.
In voltage amplifier the A.C power output is
low.
In power amplifier the A.C power output is
high.
The physical size of transistor used is
usually small and is known as low or medium
power transistor.
The physical size of transistor used is
usually large and is known as power
transistor.
In voltage amplifier the collector load has
high resistance, typically 4kΩ to 10kΩ.
In power amplifier the collector load has low
resistance, typically 5Ω to 20Ω.

90. CLASSIFICATION OF POWER AMPLIFIER

91. CONTINUE…..

94. CLASS A AMPLIFIER
• The most commonly used type of power amplifier configuration is
the Class A Amplifier. The Class A amplifier is the simplest form of
power amplifier that uses a single switching transistor in the standard
common emitter circuit configuration as seen previously to produce an
inverted output. The transistor is always biased “ON” so that it
conducts during one complete cycle of the input signal waveform
producing minimum distortion and maximum amplitude of the output
signal.
• This means then that the Class A Amplifier configuration is the ideal
operating mode, because there can be no crossover or switch-off
distortion to the output waveform even during the negative half of the
cycle

95. TYPES OF CLASS A AMPLIFIER
• Single stage
1. Series Fed Class A
• Transformer Coupled Amplifier
• Darlington Amplifier

96. SERIES FED CLASS A AMPLIFIERThe simple fixed-bias circuit
connection shown in the figure
below can be used to
discuss the main features of
a series fed class A amplifier.
The only differences between
this circuit and the small-signal
version considered previously
are that the signals handled by
the large-signal circuit are in the
range of volts and the transistor
used is a power transistor that
is capable of operating in the
range of a few to tens of watts.

97. OPERATION • Suppose Input is not given
then through biasing IB Current
is flow, Consequences Ic will
flow so we get VCE voltage .
• Now decide a value of RB that
can operate a transistor in
active region, So Q point will
be in middle
• When we give an input then
current will be change and
voltage drop across Rc is
increased So collector current
will be in 360 degree

98. NEED OF TRANSFORMER IN CLASS A
AMPLIFIER
• One of the main applications for audio frequency transformers is in
impedance matching. Audio transformers are ideal for balancing
amplifiers and loads together that have different input/output
impedances in order to achieve maximum power transfer.
• We know that for a transformer, the ratio between the number of coil
turns on the primary winding (NP) to the number of coil turns on the
secondary winding (NS) is called the “turns ratio”. Since the same
amount of voltage is induced within each single coil turn of both
windings, the primary to secondary voltage ratio (VP/VS) will therefore
be the same value as the turns ratio.

99. TRANSFORMER COUPLED CLASS A
AMPLIFIER

100. CLASS B PUSH-PULL AMPLIFIER

101. DISTORTION
• Types of Distortion
• 1. Frequency Distortion
• 2. Phase Distortion
• 3. Amplitude Distortion

102. QUESTIONS
• Compare voltage amplifier and power amplifier.
• Compare class A, B, AB and C amplifiers.
• Draw the circuit of class B push-pull amplifier and explain its working.
• Explain different types of distortions occurred in amplifier.

103. •ThankYou