Physics · Ch 16 — Semiconductor Devices

OR Gate

16.5.2

OR Gate

The OR gate has two (or more) inputs and a single output, and represents what is sometimes called LOGICAL ADDITION. Its output Y is 1 (high) whenever ANY ONE of its inputs is 1, or when more than one input (or all of them) are 1 simultaneously -- in other words, Y is 0 (low) in exactly the single case where EVERY input is 0. For the standard two-input case, its Boolean expression is $Y=A+B$ (Fig. 16.28), where the '+' symbol here denotes the logical OR operation, not ordinary arithmetic addition (so $ …

Figure 16.28Fig. 16.28: OR gate symbol

Drawn by us to help you understand the concept clearly, and verified to make sure it's accurate. For exams, practice from your textbook's own diagram.

What this figure shows. A curved, shield- or D-shaped body with a distinctly CONCAVE (curved-inward) flat/back edge on the input side and a POINTED, curved-outward tip on the output side -- the standard OR-gate shape. Two separate input lines (A and B) enter the concave back edge from the left, and a single output line (labelled $Y=A+B$ ) leaves the pointed tip on the right -- this curved-back, pointed-front outline is what visually distinguishes an OR gate from an A …

Table T16.28Truth table for the two-input OR gate, printed alongside Fig. 16.28's symbol, showing all four possible combinations of inputs A and B and the resulting output Y, confirming that Y is 0 in exactly one row (both inputs low) and 1 in every other row

Input A | Input B | Output Y

0 | 0 | 0

0 | 1 | 1 …

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