OR Gate
OR gates are basic logic gates, and are available in TTL and CMOS ICs logic families. The standard 4000 series CMOS IC is the 4071, which includes four independent two-input OR gates.
The TTL device is the 7432. There are many offshoots of the original 7432 OR gate, all having the same pinout but different internal architecture, allowing them to operate in different voltage ranges and/or at higher speeds. In addition to the standard 2-input OR gate, 3- and 4-input OR gates are also available.
In the CMOS series, these are:
4075: triple 3-input OR gate
4072: dual 4-input OR gate
Variations include:
74LS32: quad 2-input OR gate (low power Schottky version)
74AC32: quad 2-input OR gate (advanced CMOS version) - similar to 74HC32, but with significantly faster switching speeds and stronger drive
74HC32: quad 2-input OR gate (high speed CMOS version) - has lower current consumption/wider voltage range
74LVC32: low voltage CMOS version of the same.
Analytical representation
f(a,b)=a+b-a*b is the analytical representation of OR gate:
f(0,0) = 0+0-0*0 = 0
f(0,1) = 0+1-0*1 = 1
f(1,0) = 1+0-1*0 = 1
f(1,1) = 1+1-1*1 = 1
OR gates with many inputs
More efficient implementations use a cascade of NOR and NAND gates, as shown in the picture below.
OR gates with multiple inputs are designated with the same symbol, with more lines leading in.
While direct implementations with more than three inputs are possible in logic families like CMOS, these are inefficient.
Gerbang OR
IC CMOS CD4071BE
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