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Computer Technology Transistor to computer gates http://upload.wikimedia.org/wikipedia/commons/4/4e/Diopsis.jpg

Computer • Transistor • Central Processor Unit or CPU • Motherboard ` http://en.wikipedia.org/wiki/File:Asus_a8n_VMCSM02.jpg http://upload.wikimedia.org/wikipedia/commons/4/4e/Diopsis.jpg

The Transistor • Amplifier • Remote controlled switch • It is the basic element of the computer • A modern computer core (CPU) can have over 200,000,000 transistors (200 million). http://www.flickr.com/photos/oskay/2105641530/

Transistor in digital electronics • In modern electronics most transistors are used as a switch that is controlled by an input signal. • This is accomplished by giving the transistor a large enough signal to snap it on completely or… • giving it a small enough signal to turn it off. • Commonly these states (on/off) are represented by a zero (off) or one (on).

Transistors

Transistors:common circuits for computers • Transistors are used to form many basic circuits in computers. • These are the five basic circuits: • Not • AND • NAND (Not AND) • OR • NOR (Not OR) • They are named after the logic function they provide.

NOT gate • Also called a inverter • It inverts the input

Not gate using a NPN transistor If Input A is off then the gate is off and VCC supplies power to the Output Q.

Not gate using a NPN transistor If Input A is on then the gate is on and Output Q is pulled down to ground.

Transistor-AND gate • The basic AND gate has two inputs • If both inputs are high, then the output is high • Otherwise the output is low

The AND gate using PNP transistors If Input A or Input B are off then VCC turns on the Q3 and grounds the Output Q. Q3

The AND gate using PNP transistors If Input A AND Input B are on then Q3 is turned off and Output Q is pulled high. Q3

Transistor-NAND gate • The basic NAND gate has two inputs • If any inputs are high, then the output is low • Otherwise the output is high

The NAND gate using PNP transistors If Input A and Input B are on then Output Q is pulled to ground.

The NAND gate using PNP transistors If Input A or Input B are off then Output Q is pulled high.

Transistor-OR gate • The basic OR gate has two inputs • If either input is high, then the output is high • Otherwise the output is low

Transistor-OR gate with PNPs If Input A or Input B are on then Output Q is pulled high.

Transistor-OR gate with PNPs If Input A and Input B are OFF then Output Q is pulled low.

Transistor-NOR gate • The basic NOR gate has two inputs • If either input is high, then the output is low • Otherwise the output is high

Transistor-NOR gate with PNPs

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