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Techniques used in manufacturing integrated circuits

In a monolithic integrated circuit all components are fabricated by the diffusion process on a single chip of silicon . Interconnections between components are provided on the surface of the structure and external connecting wires are taken out to terminals. The vast majorityof integrated circuits are monolithic because the diffusion process is the most economicalfor mass production.

Thin Film :

Thin-film integrated circuits are constructed by depositing films of conducting materials on the surface of a glass or ceramic base.
By controlling the width and thickness of the films and by using different materials selected for their resistivity , resistors and conductors are fabricated . capacitors are produced by sandwiching a film of insulating oxide between two conducting films. Inductors are made by depositing metal film in a spiral formation . transistors and diodes are usually tiny discrete componenets connected into the circuit.

Thick-film :
Thick- film integrated circuits are sometimes referred to as printed thin-film Circuits. In this process , silk -screen printing technique are employed to create the desired circuit pattern on a ceramic substrate . The inks used are pastes which have conductive , resistive or dielectric properties. after printing, the circuits are fired at a high temperature in a furnace to fuse the films to the substrate .

INTEGRATED CIRCUITS- definition, types

TYPES OF IC :

An integrated Circuits (IC) Consists of several interconnected transistors , resistors , and so on, all contained in one all small package with external connecting terminals . the circuit may be entirely self - contained , requiring only input and output connections and a supply voltage . alternatively , a few external componenets may have to be connected to make the circuit operate.

Integrated circuits may be classified in terms of their function as analog or digital. Analog ICs ( Also termed linear ICs ) may be amplifiers , voltage regulators, and so on. digital ICs ( logic gates and counting circuits) contain transistors that are normally either in a switched - off or switched - on state.

The Techniques used in manufacturing integrated circuits provide another method of classification . The major IC manufacturing technique is termed as monolithic . other fabrication techniques are thin - film , thick-film and hybrid.

The Three - Input Adder With Truth table

It is possible To construct a complete adder without the use of half adders . The circuit has three inputs : A, B and carry C. The Output Carry C' in a serial system is delayed one synchronizing interval T and then becomes the input carry C . From The truth Table we Can verify thet the Boolean expressions for the sum S and the carry C' are given by

By Algebraic manipulation these expressions may be transformed into a number of different forms . In particular it turns out that

These expressions can also be verified from the truth table . The three - input adder is considered

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What is a P-N junction Diode ?

Definition Of P-N Junction diode?

CLICK HERE FOR HOW P-N JUNCTION DIODE WORKS

STUDY OF DECODER COUNTER IC 74LS90

Function Description :

The LS90 is a 4 bit ripple type decode counter . it consists of four master / slave flip flops which we alternative connnected to provide a divide by two - section and a divide by five section .

Each station has a separate clock input with initiate state change of the counter on high to low clock transition state changes of the counter output do not occurs simultaneously because a interval ripple delay.

Therefore decoded output signals are subject to decoding spykes and should not be used for clock or strobes. the Qo Output is designed and specified to drive the rated fan-out plus the CPI input of Device

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