Electronic Devices and Circuits: A Practical Approach

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Electronic Circuits & Devices
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Contents
Introduction......................................................................................................................................5
LO1..................................................................................................................................................6
1.1................................................................................................................................................6
1.2................................................................................................................................................8
1.3................................................................................................................................................9
1.4..............................................................................................................................................10
LO2................................................................................................................................................12
2.1..............................................................................................................................................12
2.2..............................................................................................................................................13
2.3..............................................................................................................................................14
2.4..............................................................................................................................................17
LO3................................................................................................................................................19
3.1..............................................................................................................................................19
3.2..............................................................................................................................................25
3.3..............................................................................................................................................28
LO4................................................................................................................................................31
4.1..............................................................................................................................................31
4.2..............................................................................................................................................35
4.3..............................................................................................................................................38
4.4..............................................................................................................................................43
Conclusion.....................................................................................................................................50
References......................................................................................................................................51
2

List of Figures
Figure 1: Amplifier circuit...............................................................................................................9
Figure 2: Fourier Analysis results..................................................................................................10
Figure 3: Practical results..............................................................................................................11
Figure 4: Simulation results...........................................................................................................11
Figure 5: CE Amplifier with feedback..........................................................................................15
Figure 6: Test result.......................................................................................................................15
Figure 7: CE without feedback circuit...........................................................................................16
Figure 8: Test result.......................................................................................................................16
Figure 9: CE with feedback circuit................................................................................................17
Figure 10: Magnitude vs. Frequency.............................................................................................17
Figure 11: Phase Gain vs. Frequency............................................................................................18
Figure 12: CE without feedback....................................................................................................18
Figure 13: Wein-Bridge Circuit.....................................................................................................20
Figure 14: Colpitts Oscillator circuit.............................................................................................22
Figure 15: Circuit...........................................................................................................................23
Figure 16: Wein-Bridge Oscillator circuit.....................................................................................25
Figure 17: Testing Results.............................................................................................................26
Figure 18: Colpitts Oscillator circuit.............................................................................................27
Figure 19: Collpitts Testing Results..............................................................................................28
Figure 20: Practical Result.............................................................................................................28
Figure 21: Simulation Result.........................................................................................................29
Figure 22: Practical Result.............................................................................................................29
Figure 23: Simulation Result.........................................................................................................30
Figure 24: Characteristics Datasheet.............................................................................................31
Figure 25: Characteristics Datasheet.............................................................................................32
Figure 26: Characteristics Datasheet.............................................................................................33
Figure 27: : Characteristics Datasheet...........................................................................................34
Figure 28: : Electrical Characteristics Datasheet...........................................................................35
Figure 29: Output Graphs..............................................................................................................38
Figure 30: Transistor Output Graphs.............................................................................................39
3

Figure 31: : Op-Amp Output Graphs.............................................................................................40
Figure 32: Power Supply Output Graphs.......................................................................................41
Figure 33: Transistor Amplifier Output Graphs............................................................................42
Figure 34: Diode Testing Circuit...................................................................................................43
Figure 35: : Diode Testing Result..................................................................................................43
Figure 36: Diode Testing Result Graph.........................................................................................44
Figure 37: Transistor Testing Circuit............................................................................................44
Figure 38: Transistor Testing Result Graph..................................................................................45
Figure 39: Transistor Testing Result Graph (Input + Output).......................................................45
Figure 40: Op-Amp Testing Circuit..............................................................................................46
Figure 41: : Op-Amp Testing Result.............................................................................................47
Figure 42: : Power Supply Testing Circuit....................................................................................47
Figure 43: Power supply testing results.........................................................................................48
Figure 44: Transistor Amplifier Testing Circuit............................................................................49
Figure 45: Transistor Amplifier Testing Result.............................................................................49
4

Introduction
In this report, it is being discussed regarding the operational characteristics of the circuits of the
amplifiers which involve various classes of power amplifiers and performance characteristics of
the amplifiers have also been described. In this, it has been discussed about the feedback and the
types of feedbacks & its effects on the performance of the amplifiers. Various operations &
applications related to the oscillators have been discussed and various testing methods are used
for the electronic devices & circuits. Various tests have been performed for analyzing &
comparing virtual & practical results.
5

LO1
1.1
Power Amplifiers
Power amplifier is that amplifier which increases the amplitude of any signal and it makes the
signal very strong as compared to the original signal. These amplifiers are commonly used and
are present in various circuits and characteristics of power amplifier are output, gain of signal,
efficiency & linearity and the power amplifiers generates accurate output (Kargarrazi et al.
2016).
Power amplifiers are classified on the basis of the mode of operations:
 Class A Amplifier
 Class B Amplifier
 Class AB Amplifier
Characteristics of class A amplifier
 It is considered as high gain amplifier which is having very high linearity
 Angle of conduction in these amplifiers is 360 degree, amplifier is active for the whole time
and uses all the input signals.
 As the one bias of this amplifier does not switch off at any time due to which these amplifiers
are able to provide signals of high frequency.
 They are very simple to construct with the minimum parts
 As they remain conductive all the time due to which there is the loss of power very high
 It requires high space for heat sink
 The efficiency of these amplifiers is in the range of 25-30%
6

These amplifiers are more appropriate for the outdoor events of the musical systems because in
this whole waveform is reproduced without cutting off which results in clear & linear sound.
Distortions are very less in these amplifiers.
Characteristics of class B amplifier
 These amplifiers are constructed by using 2 active devices are conducting half of the cycle
and these devices give the combined current to the load.
 Applications As there are 2 conducting devices in this amplifier each gets biased at the
positive & negative end of the cycle of sine waves. The overall result is the combined result
of both the cycles.
 Efficiency of these amplifiers is more than 60%.
 It contains crossover distortion because when the half-cycle is completed b 1 device, then
other devices have to provide the exact power simultaneously as the 1 device complete its
cycle.
Applications
These type of amplifiers are seen in design associated with the low cost
Characteristics of class AB amplifiers
 It is the approach used for overcoming the distortion in the circuits.
 It consists of the properties of both the amplifiers of class A and class B so it uses
intermediate angle of conduction.
 It is same as class B amplifier, it contains 2 devices which are biased at each end of the half-
cycle and remain on and after completing one cycle some conductance is present in the
circuit and they also conduct I put to another cycle due to which distortion is minimized.
Applications
7

These types of amplifiers are present in hi-fi systems
1.2
Performance characteristics of class B amplifiers
 Location of operating point is near the cut off voltage
 Current flows only in the one half of the circuit
 In the absence of no input signal then collector current is 0
 Maximum efficiency of collector which is possible is around 50%
 Maximum efficiency of overall which is possible is around 50%
 The output of a.c power is very large
Performance characteristics of class A amplifiers
 Coupling technique of transformer helps in enhancing the efficiency of the amplifier to a
large extent.
 Good impedance is provided between the load & output to improve the efficiency
 DC Power is wasted as current flows in a load of resistive
 Power is emitted in the heat form
 Special arrangement is needed for coupling the load in the amplifier by the appropriate
transformers
Performance characteristics of class AB amplifiers
 It is the combination of the class A and class B amplifier
 In this configuration every complementary element are biased slightly in the active region
 Overlap exists between the centre point of on and off.
8

 Distortion is reduced to 1% which is very low and can also further reduce to 0.1% by
increasing the dissipation of the power
 Tradeoff is greater than the 180 degree
 It is considered a commonly used approach in the class of amplifiers (Ravi 2018).
1.3
S1
Key = Space
C1
100nF
R1
10kΩ
U1
3554BM
6
5
7
2
1
R2
10kΩ
VCC
15V
VEE
-15V
R3
100kΩ
C2
110pF
XSC1
A B
Ext Trig
+
+
_
_ + _
V2
1 Vpk
1kHz
0°
Figure 1: Amplifier circuit
9

Figure 2: Fourier Analysis results
1.4
Test Analysis
Practical results
10

Figure 3: Practical results
Simulation Result
Figure 4: Simulation results
11

LO2
2.1
There are two types of feedback in the amplifiers circuits:
 Negative feedback
 Positive feedback
Negative feedback
Negative feedback amplifiers are those amplifiers which subtract some fraction of output from
the input such that the negative feedbacks are able to prevent the actual signal. Negative
feedback is used for improving the performance in terms of gaining the stability, linearity of the
signal, response of frequency and step response it also helps in minimizing the variations of the
sensitivity-parameter. This is the reason for which various control systems & several amplifiers
use negative feedback (Costa, 2018).
Negative feedback contains three elements such as:
 Gain of amplifier (AOL)
 Feedback network (β) is present in the amplifier which is used for sensing the output & it
transforms these signals into another form by the process of attenuation and filtering
 It contains a summing circuit which acts as subtracting and is used in combining the input &
the output which is transformed.
Equation
Gain(G)=V out / V ∈¿
G∗Vin=Vout
G ( Vin−βout )=Vout
G .Vin−β . G .Vout=Vout
12