Introduction to IC

2011-09-07T00:18:00.000-07:00

Integrated Circuit

A collection of one or more gates fabricated on a single silicon chip is called an integrated circuit (IC).
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Generations of Integration Circuits

SSI (Small Scale Integration)

MSI (Medium Scale Integration)

LSI (Large Scale Integration)

VLSI (Very Large Scale Integration)

VLSI

VLSI, or Very Large Scale Integration refers to a technology through which it is possible to implement large circuits in silicon - circuits with up to a million transistors. The VLSI technology has been successfully used to build microprocessors, signal processors, memories.

The miniaturization of hand held device is a great example of VLSI.

Challenges in designing an IC

Small Size

High Speed

Less Power Dissipation

Basic steps in IC fabrication

Introduction to MOSFET

2011-07-17T03:48:00.000-07:00

Metal Oxide Semiconductor Field Effect Transistors ( MOSFET )

A metal-oxide-semiconductor field-effect transistor (MOSFET) has three terminals, source, gate, and drain. In a p-MOSFET (or n-MOSFET), both the source S and drain D are n-type (or p-type) and the substrate between them is p-type (or n-type). The gate and the p-type substrate is insulated by a thin layer of . Due to this insulation, there is no gate current to either the source or drain.

n In an n-channel MOSFET, the channel is made of n-type semiconductor, so the charges free to move along the channel are negatively charged (electrons).

n In a p-channel device the free charges which move from end-to-end are positively charged (holes).

Basic MOSFET (n-channel)

n The gate electrode is placed on top of a very thin insulating layer.

n There are a pair of small n-type regions just under the drain & source electrodes.

n If apply a +ve voltage to gate, will push away the ‘holes’ inside the p-type substrate and attracts the moveable electrons in the n-type regions under the source & drain electrodes.

n Increasing the +ve gate voltage pushes the p-type holes further away and enlarges the thickness of the created channel.

n As a result increases the amount of current which can go from source to drain — this is why this kind of transistor is called an enhancement mode device.

Cross-section and circuit symbol of an n-type MOSFET

Basic MOSFET (p-channel)

n PMOS behave in similar way, but they pass current when a -ve gate voltage creates an effective p-type channel layer under the insulator.

Types of MOSFET

Electronics

Introduction to IC

Introduction to MOSFET