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Physics · Ch 16 — Semiconductor Devices

NOT Gate

16.5.1

NOT Gate

The NOT gate is the most basic logic gate of all: it has exactly ONE input and ONE output, and simply produces the NEGATED (inverted) version of whatever is applied at its input -- if the input is 0 (low), the output is 1 (high); if the input is 1 (high), the output is 0 (low). Because of this behaviour, the NOT gate is also commonly called an INVERTER. Its Boolean expression is written Y=X‾Y=\overline{X}, where the overline denotes logical negation ('NOT X'); its circuit symbol (Fig. 16.27) is a triangle followed by a small circle ('bubble') at its output tip, the bubble …

Figure 16.27Fig. 16.27: NOT gate symbol
Fig. 16.27 — Fig. 16.27: NOT 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 single triangle pointing to the right, representing an amplifier/buffer stage, with a single input line entering the flat (left) side of the triangle and a single output line leaving its pointed (right) vertex; at the output vertex, a small open CIRCLE ('bubble') is drawn touching the tip of the triangle -- this small circle at the output is the standard symbol that specifically denotes logical inversion/negation, distinguishing the NOT gate's symbol from a plain (non-inverting) buffer …

Table T16.27Truth table for the NOT gate, printed alongside Fig. 16.27's symbol, listing the single input column X and its corresponding negated output column Y for both possible input states of this one-input, one-output inverter

Input X | Output Y

0 | 1 …

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