Computer Technology

©2010 Akula LLC, Jeremy R. Hertzberg, BS CMPE

Computer TechnologyTransistor to computer gates

http://upload.wikimedia.org/wikipedia/commons/4/4e/Diopsis.jpg


ComputerTransistorCentral Processor Unit or CPUMotherboard

http://upload.wikimedia.org/wikipedia/commons/4/4e/Diopsis.jpghttp://en.wikipedia.org/wiki/File:Asus_a8n_VMCSM02.jpg

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The Transistor

AmplifierRemote controlled switchIt is the basic element of the

computerA 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 gateAlso called a

inverterIt inverts the

inputNOT gate

Input A Output Q0 11 0

http://en.wikipedia.org/wiki/File:Not-gate-en.svg


Not gate using a NPN transistor

NOT gate

Input A Output Q

0 1

1 0

If Input A is off then the gate is off and VCC supplies power to the Output Q.


Not gate using a NPN transistor

NOT gate

Input A Output Q

0 1

1 0

If Input A is on then the gate is on and Output Q is pulled down to ground.


Transistor-AND gateThe basic AND gate has two

inputsIf both inputs are high, then the

output is highOtherwise the output is low

AND gate Input A Input B Output Q

0 0 00 1 01 0 01 1 1

http://en.wikipedia.org/wiki/File:AND_ANSI_Labelled.svg


The AND gate using PNP transistors

AND gateInput A Input B Output Q

0 0 00 1 01 0 01 1 1

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

AND gateInput A Input B Output Q

0 0 00 1 01 0 01 1 1

If Input A AND Input B are on then Q3 is turned off and Output Q is pulled high. Q3


Transistor-NAND gateThe basic NAND gate has two

inputsIf any inputs are high, then the

output is lowOtherwise the output is high

NAND gateInput A Input B Output Q

0 0 10 1 11 0 11 1 0

http://en.wikipedia.org/wiki/File:NAND_ANSI_Labelled.svg


The NAND gate using PNP transistors


0 0 10 1 11 0 11 1 0

If Input A and Input B are on then Output Q is pulled to ground.


The NAND gate using PNP transistors


0 0 10 1 11 0 11 1 0

If Input A or Input B are off then Output Q is pulled high.


Transistor-OR gateThe basic OR gate has two inputsIf either input is high, then the

output is highOtherwise the output is low

OR gateInput A Input B Output Q

0 0 00 1 11 0 11 1 1

http://upload.wikimedia.org/wikipedia/commons/4/4c/Or-gate-en.svg


Transistor-OR gate with PNPs


0 0 00 1 11 0 11 1 1

If Input A or Input B are on then Output Q is pulled high.


Transistor-OR gate with PNPs


0 0 00 1 11 0 11 1 1

If Input A and Input B are OFF then Output Q is pulled low.


Transistor-NOR gateThe basic NOR gate has two

inputsIf either input is high, then the

output is lowOtherwise the output is high

NOR gateInput A Input B Output Q

0 0 10 1 01 0 01 1 0

http://en.wikipedia.org/wiki/File:NOR_ANSI_Labelled.svg


Transistor-NOR gate with PNPs

NOR gateInput A Input B Output Q

0 0 10 1 01 0 01 1 0

Computer Technology

Documents

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