Semiconductors are materials having electrical conductivity between that of conductors and insulators. They can be elements like silicon,germanium etc or compounds like gallium arsenide,cadmium selenide etc. Technically semiconductors are characterized by a low band gap of few electron volts between valence and conduction bands.
Showing posts with label Analog Electronics - 2018 ODD SEM. Show all posts
Showing posts with label Analog Electronics - 2018 ODD SEM. Show all posts
Non-inverting Amplifier - Operational Amplifier
In non-inverting amplifier configuration input voltage(VIN) is applied at the non-inverting input terminal of an op-amp. The feedback is applied at the inverting input terminal drawing current from the output through a potential divider network. This is shown in the following circuit diagram.
The gain of the non-inverting amplifier can be derived by applying the concept of virtual ground and Kirchoff Current Law at inverting and non-inverting terminals as follows.
Applying KCL at node V- and taking the fact that virtually no current flows into the op-amp,
Applying the concept of virtual ground,
But ,
Therefore,
Substituting Equation (2) in Equation (1),
Therefore voltage gain AV of the non-inverting amplifier is given by,
Instrumentation Amplifier - Op Amp
Instrumentation amplifier is a type of differential amplifier with input buffer stages. Input buffer stages aids in impedance matching with the previous stage. Instrumentation amplifiers are generally used in industrial and scientific measurements. Instrumentation amplifier has such useful features as low offset voltage,high CMRR,high input impedance, high gain etc. The circuit diagram of an instrumentation amplifier is shown below,
The above circuit produces an output voltage (Vout) proportional to the difference between input voltages((V1-V2).In the circuit diagram two op amps are shown as input buffers. But gain of the input buffers is not unity due to the presence of resistances R1 and Rg. Op amp at the output stage is wired as a standard differential amplifier.R2 is the input resistor and R3 is connected from output of the output op-amp to its inverting input of the op amp.
The voltage gain of the instrumentation amplifier is given by the expression,
Voltage Gain G = (VO/(V1-V2))
= (1+2R1/Rg)(R3/R2)
Instrumentation amplifiers are used where high sensitivity, accuracy and stability are required.High gain accuracy can be achieved by using precision metal film resistors for all the resistances.
As high negative feed back is employed, the instrumentation amplifier has a good linearity. The output impedance is typically in the range of few milli ohms.
ANALOG ELECTRONICS - III INTERNAL TEST
Analog Electronics - 4BPH5C1
III Internal Test
Time : 2.5 Hrs Marks: 40
PART - A 5 x 2 = 10
1.What is negative feedback?
2.State Barhausen criterion for obtaining sustained oscillations in oscillators.
3.List out the characteristics of an ideal Op Amp.
4.Draw the symbol of an Op Amp.
5.Define CMRR.
PART - B 2 x 5 = 10
7.Explain an op-amp non inverting amplifier with neat circuit diagram.
PART - C 2 x 10 = 20
9.Explain an op-amp integrator and differentiator with necessary wave forms.
Stability Factor and Its Importance
The rate of change of collector current IC with respect to the collector leakage
current ICBO is called stability factor, denoted by S.
Stabilization of operating point is important due to temperature dependence of Ic, individual variations of transistor parameters and thermal runaway.
Hybrid Parameters - h Parameters
The hybrid parameters determine transistor amplifier characteristics such as voltage gain, current gain, input and output impedance etc.Every linear circuit can be analyzed as two port networks.Four parameters called hybrid parameters or h-parameters can be used to describe these networks.One parameter is measured in ohm and another parameter is measured in mho and other two parameters are dimensionless.As these parameters have mixed dimensions they are called hybrid parameters.
ANALOG ELECTRONICS - II INTERNAL TEST
Analog Electronics - 4BPH5C1
II Internal Test
Time : 2.5 Hrs Marks: 40
PART - A 5 x 2 = 10
1.Draw the symbol of a PNP and NPN transistor.
2.Define current gain in CE mode.
3.What is stability factor? Give its importance.
4.What are h parameters?
5.Give the difference between voltage and power amplifier.
PART - B 2 x 5 = 10
2.Describe AC and DC equivalent circuits of CE transistor amplifier.
PART - C 2 x 10 = 20
2. Explain the working of an RC coupled CE amplifier. List out its merits and drawbacks.
Analog Electronics - I Internal Test
Analog Electronics - 4BPH5C1
I Internal Test
Time : 2 Hrs Marks: 40
PART - A 5 x 2 = 10
1.What are extrinsic semiconductors?
2.What is a crystal diode?
3.Define ripple factor.
4.Define current gain of a transistor in CC mode.
5.Define operating point of a transistor.
PART - B 2 x 5 = 10
2. Derive relation between alpha and beta.
PART - C 2 x 10 = 20
2.Write an essay on load line analysis of transistor circuits.
Analog Electronics - Syllabus
III YEAR – V
SEMESTER
COURSE CODE: 4BPH5C1
CORE COURSE IX – ANALOG ELECTRONICS
Unit
I SEMICONDUCTOR DIODES AND
REGULATED POWER SUPPLIES
Semiconductor diode – Crystal
Zener diode – characteristics – Voltage regulator –
Regulated power supply – Problems.
Unit
II TRANSISTORS
AND TRANSISTOR BIASING
Transistor action – CB, CE & CC modes – Comparison –
Amplifier in CE arrangement – Load line analysis – Cut – off and Saturation –
Power rating – Application of CB amplifier.
Transistor biasing – Various methods of transistor
biasing: base resistor, feedback resistor, voltage divider methods – Hybrid
parameters – Determination of h parameters – Analysis of a transistor CE
amplifier using h parameters.
Unit III AMPLIFIERS
– SINGLE STAGE & MULTISTAGE
Single stage amplifier – Phase reversal – DC & AC
equivalent circuits – Load line analysis – Voltage gain – Classification of
amplifiers – Input impedance of an amplifier.
Multistage transistor amplifier – RC, transformer, direct
coupled amplifiers – Comparison of different types of amplifiers.
Unit
IV AUDIO AMPLIFIERS AND
OSCILLATORS
Transistor audio power amplifier – Difference between
voltage and power amplifiers – Performance quantities of power amplifiers –
Classification of power amplifiers – Expression for collector efficiency –
Class A amplifier – Push – Pull amplifier – Heat sink.
Feedback principle – Negative and positive feedback –
Current gain with negative feedback – Emitter follower – DC analysis – Types of
oscillations – Undamped oscillations – Colpitt, Hartley, Phaseshift Oscillator.
Unit
V OP
AMPS
OP AMP: characteristics,
OP AMP biasing – Non – inverting & Inverting amplifiers – Applications of
OPAMP – adder, subtractor, differentiator, integrator – waveforms study, scale
changer and sign changer – Instrumentation amplifier – Voltage level detector.
OP AMP signal
generators: Phase shift, Colpitts', Hartley, Square wave and triangular
wave generators.
Books
for Study
1.
V.K.Mehta, Principles of Electronics, S.Chand & Co Ltd.,10th Edition 2007.
2.
R.S.Sedha – Text Book of Applied Electronics, S.Chand & Co Ltd., II Edition 2004.
Books
for Reference
1.
B.L. Theraja – Basic Electronics – S. Chand & Co, V Edition 2009.
2.
Malvino & Leach – Transistor Approximations – International Publication –
2000.
Triangular Wave Generator Using Op-Amps
A triangular wave generator using op-amps can be realized by cascading the output of an op-amp square wave generator to the input of an active integrator. Such an implementation is shown in the following circuit diagram.
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| Triangular Wave Generator |
Working and Circuit Analysis
Here the first op-amp is wired up as a comparator at the non-inverting input. If V+ is greater than V- then the output voltage V' will swing to +Vcc and to -Vcc if V+ is less than V- . When the circuit is switched on assume the output voltage is +Vcc and the capacitor C begins charging through the feedback resistor R with the time constant RC. As a result V- increases with time and when it becomes greater than V+ the output voltage swings to the negative rail voltage -Vcc. Now the capacitor is is discharged through R. When the voltage becomes less than -Vcc the output voltage swings back to +Vcc and the cycle begins again generating square wave.
The output of square wave generator V' is fed into the inverting input of second op-amp wired as an active integrator through the resistance R3 .
A triangular wave is generated when a capacitor is charged and discharged by a constant current source. Let V' be hight at +Vcc. This causes a constant current +Vcc/R3 through C in the integrator part to drive Vout negative linearly. When V' is low at -Vcc it forces a constant current -Vcc/R3 through C to drive Vout positive linearly. The frequency of the triangular wave is same as that of square wave and given by,
for the special case R1 = R2.
The output of square wave generator V' is fed into the inverting input of second op-amp wired as an active integrator through the resistance R3 .
A triangular wave is generated when a capacitor is charged and discharged by a constant current source. Let V' be hight at +Vcc. This causes a constant current +Vcc/R3 through C in the integrator part to drive Vout negative linearly. When V' is low at -Vcc it forces a constant current -Vcc/R3 through C to drive Vout positive linearly. The frequency of the triangular wave is same as that of square wave and given by,
Square Wave Generator Using Op-Amp
A square wave generator's output oscillates between two unstable states with a constant frequency prescribed by the circuit parameters. An op-amp implementation of square wave generator is shown in the following circuit diagram.
Working and Circuit Analysis
 |
| Square Wave Generator Using Op-Amp |
Here the op-amp is wired up as a comparator at the non-inverting input. If V+ is greater than V- then the output voltage Vout will swing to +Vcc and to -Vcc if V+ is less than V- . When the circuit is switched on assume the output voltage is +Vcc and the capacitor C begins charging through the feedback resistor R with the time constant RC. As a result V- increases with time and when it becomes greater than V+ the output voltage swings to the negative rail voltage -Vcc. Now the capacitor is is discharged through R. When the voltage becomes less than -Vcc the output voltage swings back to +Vcc and the cycle begins again generating square wave. The capacitor charging and discharging cycles and output waveforms are sketched below:
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| Square Wave Generator Waveforms |
Voltage at the non-inverting input is given by the divider equation:
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