Module 1
Introduction of Electronic Devices
1. PN Junction Diode characteristics & diode current
equation. Zener Diode as a voltage regulator.
1. Construction, working & characteristics of
BJT, JFET, & E-MOSFET
BJT
Introduction of Transistors
❑ 19 billion Transistors (FinFET) in iphone 15
❑ 37-38 Trillion operations per second
BJT
Introduction of Transistors
What is a Vacuum Tube?
●
An electronic device used to control the
current flowing in a circuit using a vacuum in
a sealed glass tube.
●
Basically, function wise the vacuum tube is an
older version of modern transistor.
●
Was used in early TVs and computer monitors.
●
Although, not completely obsolete, they are
still being used in radio stations, UHF TV
stations, sound amplifiers, etc.
BJT
Introduction of Transistors
❑ December 1947 at Bell Laboratories by John Bardeen and Walter
Brattain under the direction of William Shockley.
BJT
● Bipolar Junction Transistor
● 3-terminal semiconductor device
● Consisting of two P-N junctions
● Most widely used in Switching and Amplifiers.
BJT
Types of BJT
Fig: NPN Transistor
Fig: PNP Transistor
BJT
Symbols
Note: Ignore Circles
BJT
Construction (NPN BJT)
●
Made up of 2 layers of N-type materials,
sandwiching a middle layer of P-type
material.
●
Base region is lightly doped, and it is the
most important factor of the working of the
transistor. It acts as a controlling terminal.
●
Emitter is heavily doped, and collector is
moderately doped.
●
Compared to the other two regions, the
collector carries more current and generates
a larger amount of heat.
●
In order to dissipate heat, collector is made
of a larger area.
BJT
Remember Diode ?
BJT
4 Ways of Biasing
1.
JEB & JBC – Both reverse biased. Transistor does not conduct current & is in cut-off
stage.
2.
JEB & JBC – Both forward biased. Transistor conducts maximum current & is in
saturation mode.
3.
JEB forward biased & JBC reverse biased. Transistor is operating in active mode. This
configuration is useful for the purpose of amplification.
1.
JEB reverse biased & JBC forward biased. This is the inverse mode of operation of the
transistor. Transistor conducts but the current carrying capability of the transistor is very
poor. It can be used for attenuating the signals.
Working of NPN BJT
BJT
Working of NPN BJT
Must Watch video
BJT
BJT
Construction & Working of PNP BJT
BJT
Why the name Transistor?
Transfer + Resistance
Note: Explain amplification process
Configurations
BJT
• As the BJT is a 3 terminal device, there are basically 3 possible ways
to connect it within an electronic circuit with one terminal being
common to both the input and output side of circuit.
• These ways are called as configurations
• Each configuration results in different behavior of circuit.
CB Configuration: Has Voltage Gain but no Current Gain.
CE Configuration: Has both Current gain and Voltage Gain.
CC Configuration: Has Current Gain but no Voltage Gain.
BJT
1. Common Base (CB) Configuration
Input Characteristics
Input voltage: VBE
Input current: IE
Output Characteristics
Output Voltage:VCB
Output Current: IC
BJT
1. Common Base (CB) Configuration
BJT
1. Common Base (CB) Configuration
●
The ratio of change in collector current (ΔIC) to the change in emitter current (ΔIE)
when collector voltage VCB is kept constant, is called as Current amplification factor.
It is denoted by α.
For AC:
For DC:
𝛂=
𝛂=
ΔIC
ΔIE
IC
IE
Typical range: 0.980 to 0.995
at constant VCB
at constant VCB
BJT
2. Common Emitter (CE) Configuration:
Input Characteristics
Input voltage: VBE
Input current: IB
Output Characteristics
Output Voltage:VCE
Output Current: IC
BJT
2. Common Emitter (CE) Configuration:
BJT
2. Common Emitter (CE) Configuration:
BJT
2. Common Emitter (CE) Configuration
●
The ratio of change in collector current (ΔIC) to the change in base current (ΔIB) when
collector voltage VCE is kept constant, is called as Current amplification factor. It is
denoted by β.
For AC:
For DC:
β=
β=
ΔIC
ΔIB
IC
IB
Typical range: 50 to 500
at constant VCE
at constant VCE
BJT
2. Common Emitter (CE) Configuration:
O/P Characteristic of CE Configuration
BJT
3. Common Collector (CC) Configuration:
Input Characteristics
Input voltage: VBC
Input current: IB
Output Characteristics
Output Voltage:VEC
Output Current: IE
BJT
3. Common Collector (CC) Configuration:
BJT
3. Common Collector (CC) Configuration:
For all practical purpose, the characteristics of CC is taken same as
CE with corresponding voltages and currents for CC.
BJT
3. Common Collector (CC) Configuration
●
The ratio of change in emitter current (ΔIE) to the change in base current (ΔIB) when
voltage VEC is kept constant, is called as Current amplification factor. It is denoted
by 𝜸.
For AC:
For DC:
𝜸=
𝜸=
ΔIE
ΔIB
IE
IB
Typical range: 50 to 500
at constant VEC
at constant VEC
BJT
Q. Derive the relation between 𝛂,β and 𝜸.
BJT
Early Effect
BJT
Early Effect
Ideal o/p characteristic
BJT
Early Effect
Practical o/p characteristic
BJT
Early Effect
BJT
Module 2
Biasing Circuits of
BJTs
Biasing Circuits of BJTs
Consider a given amplifier
● The analysis of this amplifier can be
divided into two parts namely:
○ DC Analysis
○ AC Analysis
● Fortunately,
the
Superposition
theorem is applicable here and we can
investigate DC and AC analysis
separately.
VO
Biasing Circuits of BJTs
DC Analysis
● Involves careful selection of supply
voltage & Resistors to setup an
Operating point of an amplifier at
desired location.
● The circuits that helps us carry out
above selection are called DC
Biasing circuits.
VO
Biasing Circuits of BJTs
Quiescent (Q) point
●
A line joining saturation & cut off points, is
called as DC Load line.
●
This line, when drawn over the output
characteristic curve, makes contact at a point
called as Operating point.
●
As this point remains fixed, it's also known as
Quiescent ( motionless; quiet; still) point.
●
For an Amplifier, the Q point
should be at the center of DC
Load Line to get noise free output.
Biasing Circuits of BJTs
Types of Biasing Circuits
for BJT Amplifiers:
1. Fixed Bias Biasing
2. Modified Feedback Biasing
3. Collector to Base Biasing
4. Voltage Divider Biasing
Not in
syllabus
Biasing Circuits of BJTs
1. Fixed Bias Configuration
Bas bahut ho gaya PPT