Complete Guide to Logic Gates

Explore the fundamental components of digital electronics. Learn about the most common series: 7408 (AND), 7432 (OR), 7404 (NOT), 7400 (NAND) and 7486 (XOR).

Available Logic Gates

AND Logic Gate (Integrated Circuit 7408/74LS08)

The 7408 integrated circuit is a 2-input AND logic gate. Check its datasheet for technical details. For the output to be high (1), both inputs must be high (1), as shown in its truth table.

Configuration

2 inputs and 1 output

Boolean FunctionOutput = A AND B
Applications

Control systems, Arithmetic circuits

Truth Table

Input AInput BOutput
1
1
111

Datasheet and Diagram

Datasheet AND Logic Gate (Integrated Circuit 7408/74LS08)

OR Logic Gate (Integrated Circuit 7432/74LS32)

The 7432 integrated circuit is a 2-input OR logic gate. The output will be high (1) if at least one input is high (1), check its truth table. The datasheet contains more information.

Configuration

2 inputs and 1 output

Boolean FunctionOutput = A OR B
Applications

Detection systems, Selection circuits

Truth Table

Input AInput BOutput
11
11
111

Datasheet and Diagram

Datasheet OR Logic Gate (Integrated Circuit 7432/74LS32)

NOT Logic Gate (Integrated Circuit 7404/74LS04)

The 7404 integrated circuit is a NOT logic gate (inverter). It has 1 input and 1 output, inverting the signal. Check its truth table and datasheet for specifications.

Configuration

1 input and 1 output

Boolean FunctionOutput = NOT A
Applications

Signal inversion, Oscillators

Truth Table

Input AInput BOutput
1
1

Datasheet and Diagram

Datasheet NOT Logic Gate (Integrated Circuit 7404/74LS04)

NAND Logic Gate (Integrated Circuit 7400/74LS00)

The 7400 integrated circuit is a 2-input NAND gate (AND + NOT). The output is low (0) only if both inputs are high (1), as indicated by its truth table. Check the datasheet for more details.

Configuration

2 inputs and 1 output

Boolean FunctionOutput = NOT (A AND B)
Applications

Memory circuits (Flip-flops), Universal logic gate

Truth Table

Input AInput BOutput
1
11
11
11

Datasheet and Diagram

Datasheet NAND Logic Gate (Integrated Circuit 7400/74LS00)

XOR Logic Gate (Integrated Circuit 7486/74LS86)

The 7486 integrated circuit is a 2-input XOR gate. The output is high (1) if only one input is high (1), as seen in its truth table. The datasheet provides additional information.

Configuration

2 inputs and 1 output

Boolean FunctionOutput = A XOR B
Applications

Binary adders, Parity comparators...

Truth Table

Input AInput BOutput
11
11
11

Datasheet and Diagram

Datasheet XOR Logic Gate (Integrated Circuit 7486/74LS86)

NOR Logic Gate (Integrated Circuit 7402/74LS02)

The 7402 integrated circuit is a 2-input NOR logic gate. The output will be high (1) only if both inputs are low (0), as shown in its truth table.

Configuration

2 inputs and 1 output

Boolean FunctionOutput = NOT (A OR B)
Applications

Pulse generators, Universal logic gate

Truth Table

Input AInput BOutput
1
1
1
11

Datasheet and Diagram

Datasheet NOR Logic Gate (Integrated Circuit 7402/74LS02)

XNOR Logic Gate (Integrated Circuit 74266/74LS266)

The 74266 integrated circuit implements 2-input XNOR gates (logical equality). The output is high (1) when both inputs are equal.

Configuration

2 inputs and 1 output

Boolean FunctionOutput = A XNOR B
Applications

Equality comparators, Error detection codes

Truth Table

Input AInput BOutput
1
1
1
111

Datasheet and Diagram

Datasheet XNOR Logic Gate (Integrated Circuit 74266/74LS266)

Buffer (Integrated Circuit 7407/74LS07)

The 7407 integrated circuit contains open collector buffers. It is used to amplify or isolate digital signals without altering their logic.

Configuration

1 input and 1 output

Boolean FunctionOutput = A
Applications

Signal isolation, Interface with other voltage levels

Truth Table

Input AInput BOutput
11

Datasheet and Diagram

Datasheet Buffer (Integrated Circuit 7407/74LS07)

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How Logic Gates Work

Logic gates are electronic devices that perform basic logical operations based on Boolean algebra. They operate with binary signals (0 and 1, low and high voltage) and are the essential building blocks of all digital systems.

Active High and Active Low

An active low pin must be connected to a low logic level (0 volts) to activate, while an active high pin must be connected to a high logic level (3 or 5 volts).

Integrated Circuits

They are implemented in ICs such as those from the TTL or CMOS family, to save space and increase efficiency.

Main Applications

7408

Control systems

7432

Detection systems

7404

Signal inversion

7400

Memory circuits (Flip-flops)

7486

Binary adders