Name of the College : Noorul Islam College of Engineering
University : Anna University
Degree : B.E
Department : Electronics and Instrumentation Engineering
Subject Code/Name : EC 1254 – Linear Integrated Circuits
Document Type : Question Bank
Website : niceindia.com
Download Model/Sample Question Paper: https://www.pdfquestion.in/uploads/niceindia.com/3001-EC_1254_Linear_Integrated_Circuit.pdf
NICE Linear Integrated Circuits Question Paper
Circuit Configuration For Linear ICs :
2 Marks Questions :
Related :Noorul Islam College of Engineering XCS352 Theory of Computation M.Sc Question Bank : www.pdfquestion.in/3142.html
Unit – I
1.Mention the advantages of integrated circuits :
**Miniaturisation and hence increased equipment density.
**Cost reduction due to batch processing.
**Increased system reliability due to the elimination of soldered joints.
**Improved functional performance.
**Matched devices.
**Increased operating speeds.
**Reduction in power consumption.
2.Write down the various processes used to fabricate IC’s using silicon planar technology :
**Silicon wafer preparation.
** Epitaxial growth
**Oxidation.
**Photolithography.
**Diffusion.
**Ion implantation.
**Isolation.
**Metallisation.
**Assembly processing and packaging.
3.What is the purpose of oxidation? :
**SiO2 is an extremely hard protective coating and is unaffected by almost all reagents.
**By selective etching of SiO2, diffusion of impurities through carefully defined windows can be accomplished to fabricate various components.
4.Why aluminium is preferred for metallization? :
**It is a good conductor.
**it is easy to deposit aluminium films using vacuum deposition.
**It makes good mechanical bonds with silicon.
**It forms a low resistance contact.
5. What are the popular IC packages available? :
**Metal can package.
**Dual-in-line package.
**Ceramic flat package.
6. Define an operational amplifier :
An operational amplifier is a direct-coupled, high gain amplifier consisting of one or more differential amplifier. By properly selecting the external components, it can be used to perform a variety of mathematical operations.
7.Mention the characteristics of an ideal op-amp :
** Open loop voltage gain is infinity.
**Input impedance is infinity.
**Output impedance is zero.
**Bandwidth is infinity.
**Zero offset.
8.What happens when the common terminal of V+ and V- sources is not grounded? :
If the common point of the two supplies is not grounded, twice the supply voltage will get applied and it may damage the op-amp.
9.Define input offset voltage :
A small voltage applied to the input terminals to make the output voltage as zero when the two input terminals are grounded is called input offset voltage.
10. Define input offset current. State the reasons for the offset currents at the input of the op-amp :
The difference between the bias currents at the input terminals of the op-amp is called as input offset current. The input terminals conduct a small value of dc current to bias the input transistors.Since the input transistors cannot be made identical,there exists a difference in bias currents.
11. Define CMRR of an op-amp :
The relative sensitivity of an op-amp to a difference signal as compared to a common –mode signal is called the common –mode rejection ratio. It is expressed in decibels.
CMRR= Ad/Ac
12.What are the applications of current sources? :
Transistor current sources are widely used in analog ICs both as biasing elements and as load devices for amplifier stages.
13. Justify the reasons for using current sources in integrated circuits :
**superior insensitivity of circuit performance to power supply variations and temperature.
**more economical than resistors in terms of die area required to provide bias currents of small value.
**When used as load element, the high incremental resistance of current source results in high voltage gain at low supply voltages.
14. What is the advantage of widlar current source over constant current source? :
Using constant current source output current of small magnitude(microamp range) is not attainable due to the limitations in chip area. Widlar current source is useful for obtaining small output currents.Sensitivity of widlar current source is less compared to constant current source.
15.Mention the advantages of Wilson current source :
**provides high output resistance.
**offers low sensitivity to transistor base currents.
Unit – II
16 marks questions
1.Explain in detail the fabrication of ICs using silicon planar technology.
Ans:
*Silicon wafer preparation.
* Epitaxial growth
*Oxidation.
*Photolithography.
*Diffusion.
*Ion implantation.
*Isolation.
*Metallisation.
*Assembly processing and packaging.
2.Design an active load for an emitter-coupled pair(differential amplifier) and perform a detailed analysis to find its differential mode gain and the output resistance.
3.Design a Widlar current source and obtain the expression for output current.Also prove that widlar current source has better sensitivity than constant current source.
4. Explain the supply independent biasing technique using VBE as the reference voltage.Also, find the dependence of its output current on temperature.
Ans:
The output current is given by, Iout = VBE1 / R2 = (VT /R2) ln ( Iref / Is1 ) (Circuit diagram, self-biasing VBE reference circuit, start-up circuit to avoid zerocurrent state) Temperature co-efficient, TCF = VBE1/ VBE1 T — R/ R T
5.Explain supply independent biasing using zener-referenced bias circuit.
Also,design a temperature compensated zener-reference source.
Ans:
The output current is given by, Iout = VZ / R2 (Circuit diagram, self-biasing zener bias reference circuit, temperature compensated zener reference source