Digital Circuit 03 OR-gate
Explaination how an OR-gate works in the usual cmos technology.
The OR-gate is one of the three fundamental elements of digital electronics, together with the AND-gate and the inverter. It consists of three NMOS transistors and three PMOS transistors. One pair of NMOS and PMOS form an inverter, the rest forms an NOR-Gate. The output of the NOR is inverted to OR. That is why most integrated chips that form an OR, also have an output for the NOR: it simply does not need any more transistors, because the NOR is already created. So you need only one pin to carry out the NOR.
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Title=Digital Circuit 03 OR-gate