Linear Integrated Circuits (LIC) are electronic circuits in which all components such as transistors, resistors, diodes, and capacitors are fabricated on a single semiconductor chip and operate in the linear region. These circuits are widely used for amplification, signal conditioning, filtering, oscillation, voltage regulation, and analog computation. Due to their reliability, compact size, low power consumption, and cost effectiveness, linear ICs form the backbone of modern analog and mixed-signal systems.
Operational Amplifiers (Op-Amps)
The operational amplifier is the most important building block of linear integrated circuits. An op-amp is a high-gain, DC-coupled differential amplifier characterized by high input impedance, low output impedance, and very high open-loop gain. Ideal op-amp characteristics include infinite gain, infinite input impedance, zero output impedance, infinite bandwidth, and zero offset voltage. Practical op-amps such as the µA741 exhibit finite gain, input bias current, offset voltage, slew rate, and limited bandwidth, which must be considered in real applications.
Op-Amp Configurations and Applications
Op-amps can be configured using external feedback components to perform various linear and nonlinear operations. Common configurations include inverting amplifier, non-inverting amplifier, voltage follower, summing amplifier, difference amplifier, and integrator and differentiator circuits. Applications of op-amps include signal amplification, active filters, analog computation, instrumentation amplifiers, waveform generation, and signal conditioning in measurement systems.
Frequency Response and Compensation
The frequency response of an op-amp describes how gain varies with frequency. Important parameters include gain-bandwidth product, slew rate, and phase margin. Frequency compensation techniques are used to ensure stability and prevent oscillations in high-gain amplifier configurations. Dominant pole compensation is commonly used in internally compensated op-amps like the 741.
Comparators and Applications
Comparators are special op-amp circuits used to compare two input voltages and produce a digital output. Zero-crossing detectors, window comparators, and Schmitt triggers are widely used comparator applications. Schmitt triggers introduce hysteresis to improve noise immunity in switching circuits.
Timers and Multivibrators
The 555 Timer IC is one of the most popular linear ICs used for timing and waveform generation. It can operate in astable, monostable, and bistable modes. Applications include pulse generation, time delay circuits, frequency generation, PWM control, and oscillator circuits. The simplicity and versatility of the 555 timer make it essential in analog and digital interfacing.
Active Filters
Active filters use op-amps along with resistors and capacitors to achieve desired frequency responses without inductors. Types of active filters include low-pass, high-pass, band-pass, and band-stop filters. Key parameters include cutoff frequency, bandwidth, quality factor (Q), and gain. Active filters are widely used in communication systems, audio processing, and instrumentation.
Voltage Regulators
Voltage regulator ICs maintain a constant output voltage despite variations in input voltage or load current. Linear voltage regulators such as 78XX (positive) and 79XX (negative) series provide fixed regulated outputs, while adjustable regulators like LM317 allow variable output voltage control. Important specifications include line regulation, load regulation, ripple rejection, and thermal protection.
Data Converters
Linear ICs include analog-to-digital converters (ADC) and digital-to-analog converters (DAC), which enable interfacing between analog and digital systems. DACs convert digital signals into analog voltages or currents, while ADCs convert analog signals into digital form. Resolution, accuracy, conversion speed, and linearity are key performance parameters.
IC Fabrication Technology
Linear integrated circuits are fabricated using technologies such as monolithic ICs, thin-film ICs, thick-film ICs, and hybrid ICs. Monolithic ICs are the most widely used due to their high reliability and low cost. Fabrication involves processes such as oxidation, diffusion, ion implantation, photolithography, and metallization.
Applications of Linear Integrated Circuits
Linear ICs are extensively used in communication systems, biomedical instrumentation, industrial control, audio and video systems, power supplies, and measurement and automation systems. Their ability to process continuous-time signals makes them indispensable in real-world electronic applications.
Importance for Exams
Linear Integrated Circuits is a high-weightage subject in Anna University examinations, PhD entrance tests, GATE, and competitive technical exams. Frequently asked topics include op-amp characteristics, applications of 741, 555 timer modes, active filters, voltage regulators, and frequency response analysis.
SYLLABUS LINEAR INTEGRATED CIRCUITS L T P C 3 0 0 3
COURSE OBJECTIVES:
● To introduce the
basic building blocks of linear integrated circuits
● To learn the linear
and non-linear applications of operational amplifiers
● To introduce the
theory and applications of analog multipliers and PLL
● To learn the theory
of ADC and DAC
● To introduce the concepts of waveform generation and introduce some special function ICs
UNIT I BASICS OF
OPERATIONAL AMPLIFIERS 9
Current mirror and
current sources, Current sources as active loads, Voltage sources, oltage
References, BJT
Differential amplifier with active loads, Basic information about op-amps – ideal
Operational Amplifier - General operational amplifier stages -and internal circuit
diagrams of IC741, DC and AC performance characteristics, slew rate, Open and
closed loop configurations –MOSFET Operational Amplifiers – LF155
and TL082.
UNIT II APPLICATIONS OF OPERATIONAL AMPLIFIERS 9
Sign Changer, Scale Changer, Phase Shift Circuits, Voltage Follower, V-to-I and I-to-V converters, adder, subtractor, Instrumentation amplifier, Integrator, Differentiator, Logarithmic amplifier, Antilogarithmic amplifier, Comparators, Schmitt trigger, Precision rectifier, peak detector, clipper and clamper, Low-pass, high-pass and band-pass Butterworth filters.
UNIT III ANALOG MULTIPLIER AND PLL 9
Analog Multiplier using Emitter Coupled Transistor Pair - Gilbert Multiplier cell – Variable transconductance technique, analog multiplier ICs and their applications, Operation of the basic PLL, Closed loop analysis, Voltage controlled oscillator, Monolithic PLL IC 565, application of PLL for AM detection, FM detection, FSK modulation and demodulation and Frequency synthesizing and clock synchronization
UNIT IV ANALOG TO
DIGITAL AND DIGITAL TO ANALOG CONVERTERS 9
Analog and Digital Data Conversions, D/A converter – specifications - weighted resistor type, R-2R Ladder type, Voltage Mode and Current-Mode R - 2R Ladder types - switches for D/A converters, high speed sample-and-hold circuits, A/D Converters – specifications - Flash type – Successive Approximation type - Single Slope type – Dual Slope type - A/D Converter using Voltage-to-Time Conversion - Over-sampling A/D Converters, Sigma – Delta converters.
UNIT V WAVEFORM
GENERATORS AND SPECIAL FUNCTION ICS 9
Sine-wave generators, Multivibrators and Triangular wave generator, Saw-tooth wave generator, ICL8038 function generator, Timer IC 555, IC Voltage regulators – Three terminal fixed and adjustable voltage regulators - IC 723 general purpose regulator - Monolithic switching regulator, Low Drop – Out(LDO) Regulators - Switched capacitor filter IC MF10, Frequency to Voltage and Voltage to Frequency converters, Audio Power amplifier, Video Amplifier, Isolation Amplifier, Optocouplers and fibre optic IC
COURSE OUTCOMES: TOTAL:45 PERIODS
At the end of the
course the students will be able to
CO1 : Design linear and
nonlinear applications of OP – AMPS
CO2 : Design applications
using analog multiplier and PLL
CO3 : Design ADC and DAC
using OP – AMPS
CO4 : Generate waveforms
using OP – AMP Circuits
CO5 : Analyze special
function ICs
TEXT BOOK
1. 1.D.Roy Choudhry, Shail Jain, “Linear Integrated Circuits”, New Age
International Pvt. Ltd., 2018,
Fifth Edition. (Unit I – V)
2. 2.Sergio Franco, “Design with Operational Amplifiers and Analog Integrated Circuits”, 4th Edition, Tata Mc Graw-Hill, 2016 (Unit I – V)
REFERENCES
1. Ramakant A. Gayakwad, “OP-AMP and Linear ICs”, 4th Edition, Prentice
Hall / Pearson Education,
2015
2. Robert F.Coughlin, Frederick F.Driscoll, “Operational Amplifiers and
Linear Integrated Circuits”, Sixth Edition, PHI, 2001.
3. S.Salivahanan & V.S. Kanchana Bhaskaran, “Linear Integrated Circuits”,
TMH,2nd Edition,
4th Reprint, 2016.
UNIT IV ANALOG TO DIGITAL AND DIGITAL TO ANALOG CONVERTERS
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