Inside the Computer Transistors, Integrated Circuits - Lecture Slides | CS 1030, Study notes of Computer Science

Download Inside the Computer Transistors, Integrated Circuits - Lecture Slides | CS 1030 and more Study notes Computer Science in PDF only on Docsity! 4/3/2009 1 Chapter 16 Inside the Computer – Transistors and Integrated Circuits Electricity and Switches
modern computers are powered by electricity, using electrical signals to store and manipulate information
the components of a computer require electrical power to carry out their assigned task
electricity generates the light that shines through a computer screen, illuminating the individual pixels that make up images and letters
electricity runs the motor that spins the hard-drive disk, allowing information to be accessed
main memory and CPU employ electrical signals to store and manipulate data
bit patterns are represented by the presence or absence of electrical current along a wire Electricity Basics
electricity is a flow of electrons, the negatively charged particles in atoms, through a medium
good conductors of electricity allow for the flow of electrons with little resistance (e.g., copper, silver, gold)
other elements, especially nonmetals, are poor conductors (e.g., carbon, oxygen) Electricity Basics
electricity can be quantified in amperes or voltage
amperes gauge electron flow: 1 amp is equal to 6.24 quintillion (1018) electrons flowing past a given point each second
voltage measures the physical force produced by the flow of electrons: standard household in United States has 110 to 120 volt outlets Electricity Basics Switches
the most basic tool for controlling the flow of electricity is a switch
a switch can be flipped to connect or disconnect two wires, thus regulating the flow of electricity between them 4/3/2009 2 Switches Transistors
as we saw in Chapter 6, advances in switching technology have defined the generations of computers
1930’s – electromagnetic relays served as physical switches, whose on/off positions were controlled by the voltage to a magnet
1940’s – vacuum tubes replaced relays, which were faster (since no moving parts) but tended to overheat and burn out frequently
1948 – the transistor was developed by Bardeen, Brattain, and Shockley
a transistor is a solid piece of metal attached to a wire that serves as a switch by alternatively conducting or resisting electricity
transistors allowed for the development of smaller, faster machines at a lower cost Transistors semiconductors are metals that can be manipulated to be either good or bad conductors of electricity
the first transistors were made of germanium and gold, but modern transistors are constructed from silicon
through a process known as doping, impurities are added to a slab of silicon, causing the metal to act as an electrical switch Transistors as Switches
a PMOS transistor is positively doped, so that the switch is "closed" when there is no current on the control wire, but "opens" when current is applied Transistors as Switches an NMOS transistor is negatively doped, so that the switch is "open" when there is no current, but "closes" when there is current From Transistors to Gates
transistors can be combined to form a circuit, which controls the flow of electricity in order to produce a particular behavior
the term “gate” suggests a simple circuit that controls the flow of electricity
in the case of a NOT gate, the flow of electricity is manipulated so that the output signal is always opposite of the input signal