Logic Gates - 2

Gates are what make many of ICs, the two popular families are the 40xx CMOS and the 74xx TTL . Now 40xx come in 74HCT40xx flavors which approach the quality of an ideal gate. Entire circuits with Gates can also be also be burnt into PLDs, FPGAs and CPLDs just like you burn your CDROM. Gates can also be implemented in assembly language which a microcontroller like 8051 will understand and execute. Hardware gate circuit will operate in real time, nano seconds delay will be there due to propagation delay, gate capacitance and FET switching times etc. Software or microcontroller gates code working will depend on both propagation delay and the CPU clock speed.    

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

AND gate.

This gate ANDs the two inputs A and B, The Output is high only if A AND B both are high. There may be a AND gate with many inputs, only if all inputs are high 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 0
1 0 0
1
 		1 1


The AND 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. 
 
doc00012.html          12:33 07-Aug-04          anantha narayan delabs india
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