7400 Family Truth Tables

Basic logic gates are fundamental building blocks of digital circuits, performing logical operations on binary inputs to produce a single binary output.

The seven basic logic gates are:

Logic Gates Truth Tables

Buffer

Input	Output
0	0
1	1

NOT Gate

Input	Output
0	1
1	0

AND Gate

A	B	Output
0	0	0
0	1	0
1	0	0
1	1	1

NAND Gate

A	B	Output
0	0	1
0	1	1
1	0	1
1	1	0

OR Gate

A	B	Output
0	0	0
0	1	1
1	0	1
1	1	1

NOR Gate

A	B	Output
0	0	1
0	1	0
1	0	0
1	1	0

XOR Gate

A	B	Output
0	0	0
0	1	1
1	0	1
1	1	0

XNOR Gate

A	B	Output
0	0	1
0	1	0
1	0	0
1	1	1

Image linked from learnabout-electronics.org

Tri-state outputs (for multiplexing outputs)

_{Retrieved 11:23, 26 February 2024 (UTC) from Perplexity.io}

In a 7400-series integrated circuit, the main difference between a tri-state output and a regular output lies in the ability of the tri-state output to assume three states: high (logic 1), low (logic 0), or a high-impedance state (open circuit). This allows the output to be effectively disconnected from the rest of the circuit when not actively driving a signal. Tri-state outputs require an additional "enable" input to control whether the output is active or in the high-impedance state, providing flexibility in signal routing and preventing short circuits when multiple devices are connected to the same output line[1][3]. Regular outputs, on the other hand, typically drive signals actively without the option to disconnect from the circuit.

The tri-state output's ability to enter a high-impedance state makes it particularly useful in scenarios where multiple devices share a common output line, allowing only one device to drive the signal at a time while others remain disconnected, thus preventing signal contention and ensuring proper communication within the circuit[3].

Citations

[1] https://www.electronics-notes.com/articles/electronic_components/logic-ic-families-technologies/7400-series-ttl.php

[2] https://youtube.com/watch?v=OgV4tDxk7sY

[3] https://forum.digikey.com/t/tri-state-logic-input-outputs/25183

[4] http://www.markbereit.com/rsrc/ccdig_74ls.html

[5] https://en.wikipedia.org/wiki/7400-series_integrated_circuits