Logic Gates - 3

Gates can be combined to make combinational or sequential logic circuits. combinational circuits are a complex network of gates interconnected to evaluate a pattern of output for patterns of input. Sequential circuits use memory elements hence output patterns depend both on input patterns and the memory of history of events. An example of combinational logic circuit is a seven segment display decoder CD4511 and and example for a sequential logic circuit is CD4029 up-down counter.    

This page requires images and javascript to be enabled to try out the demo of the gates below.

OR gate.

This gate ORs the two inputs A and B, The Output is high if either A OR B is high. There may be a OR gate with many inputs, if one or more inputs are high then the output will be high.

A
Q

B



Toggle the red buttons above to apply a 'high' or 'low' to inputs A and B and watch the output Q.

Truth table.
A B Q
0
 		0 0
0 1 1
1 0 1
1
 		1 1


The OR gates can be built with diodes and transistors if you want to do it on your own. Then read more on how to do it here at play-hookey's digital section and Logic families. more on TTL here at Chipdir. 
 
doc00013.html          12:33 07-Aug-04          anantha narayan delabs india
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