Input Controls
Live Display
| A | Output (Y = A') |
|---|---|
| 0 | 1 |
| 1 | 0 |
Current Observation
When Input A is LOW (0), the output becomes HIGH (1) and the LED glows GREEN. When Input A is HIGH (1), the output becomes LOW (0) and the LED turns OFF.
Signal Flow Observation
Toggle the switch to observe signal flow. Notice how the NOT gate (inverter) inverts the logical state of Input A to generate the opposite Output Y.
Definition
A NOT gate (also called an inverter) is a fundamental digital logic gate that performs logical negation. It has only one input and one output, producing an output signal that is the inverse of its input signal.
Working Principle
The NOT gate inverts the logic level applied to its input terminal. In transistor-level logic (e.g. CMOS or TTL), when a high voltage is applied to the input, the transistor switches ON pulling the output to ground (LOW). When a low voltage is applied, the transistor switches OFF allowing the output to pull up to Vcc (HIGH).
- When Input A is LOW (0): Output Y becomes HIGH (1).
- When Input A is HIGH (1): Output Y becomes LOW (0).
Truth Table Summary
The NOT gate has 1 input and 2 possible input combinations. Input 0 yields Output 1, and Input 1 yields Output 0.
Boolean Expression
Y = A' (also written as Y = NOT A, or Y = Ā)
Industrial Applications
- Switch → NOT Gate → Lamp: The lamp turns ON when the switch is OFF and turns OFF when the switch is ON.
- Security & Emergency Alarms: Inverting sensor inputs so normally-closed (NC) safety switches generate an active alarm signal when opened.
- Signal Inversion in Digital Circuits: Inverting active-low control signals (such as Enable or Reset lines) in microcontrollers and memory modules.
- Clock Pulse Oscillators: Connecting an odd number of NOT gates in a ring configuration creates ring oscillators for clock generation.
- Logic Gate Synthesizing: Combining NOT gates with AND/OR gates to form NAND, NOR, and XOR gates.
Boolean Expression
Y = A'
The prime symbol (') represents the NOT (inversion) operation in Boolean algebra. It negates the logical value of Input A.
Boolean Algebra Properties of NOT
- Double Negation Law: (A')' = A
- Complementarity (OR): A + A' = 1
- Complement Law (AND): A · A' = 0
- De Morgan's First Law: (A · B)' = A' + B'
- De Morgan's Second Law: (A + B)' = A' · B'
Current Calculation
A = 0 → Y = 0' = 1
Switch → NOT Gate → Lamp
This demonstrates an industrial NOT gate application. The lamp turns ON when the switch is OFF and turns OFF when the switch is ON.
Click the switch on the left to toggle its state and observe how the NOT gate inverts the switch signal to control the lamp.