22-01-2016, 04:35 PM
HISTORY OF TRANSISTOR:
A transistor is a semi conductor device used to amplify and switch electronic signals and electrical power. It is composed of semiconductor material with atleast three terminals for connection to an external circuit.Today some transistors are packaged individually,but many more are found embedded in integrated circuits.
T-R-A-N-S-I-S-T-O-R = TRANsfer resisTOR
In 1947: John Bardeen, Walter Brattain and William Schokley at Bell laboratories built the first working point contact transistor (Nobel Prize in Physics in 1956)
In 1958: Jack Kylby built the first integrated circuit flip flop at Texas Instruments (Nobel Prize in Physics in 2000)
In 1925: Julius Lilienfield patents the original idea of field effect transistors
In 1935: Oskar Heil patents the first MOSFET
In 1963: Frank Wanlass at Fairchild describes the first CMOS logic gate (nMOS and pMOS)
In 1970: Processes using nMOS became dominant
In 1980: Power consumption become a major issue. CMOS process are widely adopted.
INTRODUCTION TO VLSI:
VLSI stands for VERY LARGE SCALE INTEGRATED circuits. VLSI is the process of creating integrated circuits by integrating thousands of transistors into a single chip. It is nothing but a level of integration. The field which involves packaging more and more number of logic devices into smaller and smaller die area. The Microprocessor is a common example of VLSI device.
CHIP INTEGRATION LEVELS:
SSI = small-scale integration ( upto 10 gates)
MSI = medium-scale integration ( upto 1000 gates)
LSI = large-scale integration (upto 10,000 gates)
VLSI = very large-scale integration (over 10,000 gates)
WHY VLSI?
VLSI improves the design:
– Compactness: less area, physically smaller
– Higher speed: lower parasitics (reduced interconnection length)
- Lower power consumption
- Higher reliability: improved on-chip interconnects
-significantly reduces manufacturing cost.