What is VLSI & Why we Need VLSI ?

As we all know VLSI stands for Very large scale integration. Very large scale integration  is the process of creating an integrated circuit by combining thousands of transistors into a single chip. Now the question comes why we need VLSI???? So the answer is that one of the most characteristics of information service is there increasing need for very high processing and band width. The other important characteristics is that the information service  tend  to become more personalized, which means that the information processing device must be more intelligent and also be portable to allow more mobility.

VLSI is mainly classified in two classes.

 VLSI back end – VLSI back-end includes Route, place and floor planning. Back end includes development and fabrication part. It is  too costly and time consuming process.Physical designing and layout refers to back end.

 VLSI front end – VLSI Frontend includes designing and testing part.  It uses Verilog and HDL, VHDL .RTL designing , minimizing delay and simulation refers to Front end.

VLSI

There are two important   steps . VLSI design and  designverification. VLSI design refers to  the  designing of  VLSI circuits and its implementation . Design verification is use to test the design  and verify us that the given designing is working properly or not.
 

Now, we should move towards physical and digital design of VLSI. Both are very important part of VLSI.

Digital design is divided in three steps. First is BEHAVIORAL, second is STRUCTURAL and third one is PHYSICAL design. BEHAVIORAL describes the algorithm, STRUCTURAL describes component and their connections,  PHYSICAL describes how circuit built.

In standard design cycle physical design  comes after  the circuit design. Physical design includes both design and verification and validation of layout.  At this step circuit representation is converted into geometric representation. 

                                                                                                                 

                                                                                                       Author - Trisha Jain
                                                                                                  (Intern at Silicon Mentor) 

Role of SPICE Simulator in Analog/Digital VLSI Design

As we are entering in the great era of electronics world so we need tools and techniques which can makes our work easier. One of them is SPICE.

SPICE is the acronym of “simulation program with integration circuit emphasis”. As the name suggests it is general purpose software for the simulation of different circuits. SPICE used for EDA (electronic design automation).

Now let us discuss about process of using SPICE for simulation. In this tool, circuit file is the input. For creating circuit file, programming or directly schematic can be used. Programming may be simple code in “c language” or in any other computer language while schematic is drawn according to desire circuitry in SPICE schematic window. There is library present in SPICE tool which contains the basic components used to draw a circuit. Once the circuit file is created simulation command is given to simulate it and we get response according to schematic.

SPICE

SPICE is used when we need different kinds of analysis like AC analysis, DC analysis, DC transfer curve, noise analysis, transfer function analysis, transient analysis.
Instead of using breadboard for testing a circuit we use SPICE software it makes our work efficient.

DIGITAL VERSUS ANALOG CIRCUIT

Most of the electronic industry is comprises of analog and digital circuits both plays a crucial role in electronics and electrical applications.

Now there are some points, which defines there importance comparative to each other, are given as follows :

Continuity : Analog circuit functioned on continuous signal while in digital circuits operates on discrete signals.

Flexibility : Generally analog circuits lacks in terms of flexibility while digital circuits are highly flexible as   they can modified easily by just changing the logic function.

Complexity :  Analog circuits are more complex to design then digital circuits.

Converters :  In analog circuit there is no need of converters inputs and outputs both are given in analog   form while in digital circuits analog to digital converter is required for input and digital to analog converter is needed for output.

 Noise : Analog circuits are more vulnerable to noise while digital circuits have more noise tolerance.

Author - Jyotishna Bansal

(Intern at Silicon Mentor)