in this slide you will learn what are classes of amplifiers and what is main difference between all classes of amplifier and after reading this slide you will be able to explain all clases of amplifier

1. Assignment no ;01
Topic; Amplifier Classes
Submitted by;
Abdulrehman
Submitted to;
DR Ahmad Raza

2. Amplifier
An amplifier is an electronic device or circuit which is used to increase the
magnitude of the signal applied to its input.

3. What are classes of amplifier?
AMPLIFIER CLASS DESCRIPTION CONDUCTION ANGLE Θ
Class A Conduction over the full
360° of the cycle
θ = 2π
Class B Conduction occurs over
half the cycle, i.e. for
180°
θ = π
Class AB Conduction occurs for
slightly more than half the
cycle, i.e. slightly more
than 360°
θ < θ < 2π
Class C Conduction occurs for less
than 180° of the cycle, but
this creates distortion
θ < π
Classes D to T These amplifier classes
utilise non-linear switching
techniques to improve
efficiency.
N/A

4. Class a Amplifier;
The most popular sort of power amplifier is the Class
A amplifier. Using a single transistor to produce a single inverted output
in the standard typical circuit configuration, the class A amplifier is the
simplest type of power amplifier. This is the simplest kind of power
amplifier circuit in Class A. It uses a single-ended transistor for its output
stage, with a resistive load directly connected to the collector terminal.
The output current sinks through the collector as the transistor turns on,
resulting in an eventual drop in voltage through the emitter resistance,
thus limiting the negative output capability

5. The efficiency of this type of circuit is very poor (less
than 30 percent) and produces small outputs on the
DC power supply for a large drain. Even when no input
signal is applied, the amplifier stage Class A passes the
same load current so that large heat sinks are needed
for the output transistors.
Applications of Class A Amplifier:
For outdoor music systems, the Class A amplifier is
better suitable, as the resistor reproduces the entire
audio waveform without being broken off.
The sound is also more stable and
more linear, i.e. it has much
lower distortion levels.

6. Group A Amplifier Advantages:
1.It has high accuracy thanks to the exact output copy of
the input signal.
2.High-frequency response has increased when the
activated system is on full time, i.e. no time is taken to
turn the device on.
3. There is no crossover distortion since the active unit
works for the entire input signal duration.
4. The single-ended structure can be quickly and
technically realized in class A amp.
Class A amplifier disadvantage:
1.Class A amplifier is expensive and cumbersome due to
the large power source and heat sink.
2.They've got low performance.
3.The frequency response of the transformer coupling is
not as strong

7. Class B Amplifier:
Class B is a type of power amplifier in which the active device
(transistor) for only half a cycle conducts the input signal. The
conductivity angle on a Class B amplifier is 180 °. For two or
more transistors, Class-B amps are used in such a way that only
half of the input waveform loop can be carried out by each
transistor. In its output level, also called a push pull enhancer
configuration, the power amplifiers can be equipped with two
transistors,
producing what is usually called a Class B amp,
to increase the maximum power efficiency
of the previous Class A amplifier by
decreasing waste heat power.

9. Applications:
Products working in Class B are used in linear amplifiers,
so-called because the output of the radio frequency is
equal to the input voltage square. This function avoids
the distortion of amplitude-modulated or frequency-
modulated signals going through the amplifier.
Advantages of Class B amplifier:
• High efficiency when compared to the Class A
configurations.
• Push-pull mechanism avoids even harmonics.
• No DC components in the output (in ideal case).

10. Disadvantages of Class B amplifier:
• The major disadvantage is the cross-
over distortion
• Coupling transformers increases the cost
and size.
• It is difficult to find ideal transformers.

11. Class AB amplifiers:
In order to make the amplifier more efficient than Class A but with
less distortion than Class B, Class AB amplifiers combine Class A and
Class B. This is done by bias in both transistors in such a way that
they work when the signal is close to zero (the point where class B
amplifiers introduce non-linearities).

12. As the current passes through the resistor, as defined by Ohm's law, a
voltage drop is generated across the resistor. So, we can create a voltage
divider network by placing two or more resistors in series around the
supply voltage, which generates a range of fixed voltages at our
preferred values. The simple circuit is similar to the above voltage bias
circuit in that the input waveform is performed by the transistors, TR1
and TR2 during the opposite half of the loop. That is, TR1 is positive
when VIN is positive, and TR2 is positive when VIN is negative.
Advantages:
• The class AB has a linear behavior
• The design of this amplifier is very simple
• The distortion of this amplifier is less than 0.1%
• The sound quality of this sound is very high

13. Disadvantages:
• The power dissipation of this amplifier
generates the heat and requires large
amount of heat sink
• This amplifier has low power efficiency and
the average efficiency is less than the 50%

14. Class C Amplifier:
As the collector current flows from the input signal in less than
half a loop, the power amplifier is known as the class C power
amplifier. The efficiency of the class C amplifier is high, while
the linearity is low. For class C, the driving angle is less than
180 degrees. As seen in the circuit diagram.
Resistor Rb binds to the base of transistor Q1. In a DC
load line, a biasing resistor joining the base of Q1
attempts to move the base of the transistor further
down to set the working point dc bias below the
cut-off point (ICO, which is supposed to be zero)
in the cut-off of the collector current. ICO
is the DC load line. In the active region where BJT
resides, the load line for dc is the locus of IC and VCE.

16. Inductor L1 an capacitor C1 forms a tuned circuit which is also
called a tank circuit. LC circuits are used either for generating
signals at a particular frequency, or picking out a signal at a
particular frequency from a more complex signal which extract
the required signal from the pulsed output of the transistor.
Applications of Class C Amplifier:
Class C Amplifier is used in: –
RF oscillators. RF amplifier. FM
transmitters.
Booster amplifiers. High frequency repeaters. Tuned
amplifiers.

17. Advantages of Class C Amplifier:
The advantages of Class C Amplifier are as
follows: –
• Higher efficiency.
• Best result in RF applications.
• Physical size is suitable for given power.

18. Disadvantages of Class C Amplifier:
The disadvantages of Class C Amplifier are as
follows: –
• Poor linearity.
• Not suitable for audio applications.
• Lot of noise and RF interference.
• To obtain ideal inductors and coupling
transformers it is very difficult.
• Not good dynamic range.

19. Class D Amplifier:
A Class D amplifier is an electronic amplifier in
which the amplifier components are used as
electronic switches (transistors, usually
MOSFETs, not as linear gain devices, as with
other extensions.

20. Applications of Class D amplifier:
In programs such as hand-held audio systems, mobile home
theaters, mobile phones, etc. Where all of their outputs
must be good (in terms of energy and loyalty) and size must
be as small as possible, Class-D amplifiers have been popular.
The Class D amplifier is a switching amplifier and it will drive
current but will almost have zero voltage on the switches
while the "On" state is in place. In "OFF" mode, the voltage
will go over the MOSFETs, but because of no current flow,
the switch does not need any power. Only when the leakage
currents are not taken into account during the on/off
transitions does the amplifier require power. The following
Class D amplifier measurements:

22. Advantages Class D amplifier:
A high performance of about 90 per cent is the main
advantage of the class D amplifier. The Class AB amplifier
with an efficiency of 50 to 70 percent is much greater than
its nearest analog competitor. High performance helps the
physical component to be minimized and heatsinks and
refreshments can theoretically be eliminated.
• Low heat dissipation.
• Reduced size and weight.
• High power conversion efficiency. Almost all power
drawn is supplied to the load.

23. Disadvantages of Class D amplifiers:
When the power transistor of the Class D power
amplifier is initially connected and shut off, the
potential near to the ground can fluctuate to
increase the noise level. For any cause, Class D
power amplifier speakers can be skewed.
• Requires a very clean and stable power
supply.
• The high frequency response is dependent
on the loudspeaker impedance.

24. Thank-you