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7400-Series Logic ICs Specification

1. Overview

The 7400-series is a large family of digital logic integrated circuits originally implemented in TTL (Transistor-Transistor Logic) and later expanded to include CMOS-compatible variants. These devices provide fundamental building blocks such as gates, flip-flops, counters, multiplexers, decoders, and bus transceivers.

7400-series ICs are widely used in retrocomputing, 6502/Z80 systems, glue logic, and educational designs.

2. Logic Families

Family Technology Notes
74xx TTL Original bipolar TTL
74LSxx Low-power Schottky TTL Faster, lower power
74HCTxx CMOS (TTL-level inputs) Ideal for mixed systems
74HCxx CMOS Wide voltage range
74ACTxx Advanced CMOS TTL-level Very fast

3. Electrical Characteristics (Typical)

Parameter TTL CMOS
VCC 5 V 2-6 V (5 V typical)
Input HIGH ≥ 2.0 V ≥ 0.7xVCC
Input LOW ≤ 0.8 V ≤ 0.3xVCC
Fan-out ~10 Very high
Power consumption Higher Lower

4. Standard Package Types

Package Pins Notes
DIP 14, 16, 20 Breadboard-friendly
SOIC 14, 16, 20 Surface-mount
TSSOP 14, 16 Compact SMT

5. Common Logic Categories

5.1 Basic Logic Gates

IC Function
7400 Quad 2-input NAND
7402 Quad 2-input NOR
7404 Hex inverter
7408 Quad 2-input AND
7432 Quad 2-input OR
7486 Quad 2-input XOR

5.2 Latches and Flip-Flops

IC Function
7474 Dual D-type flip-flop
7473 Dual JK flip-flop
7475 Quad latch
74175 Quad D-type FF

5.3 Counters and Registers

IC Function
74161 Synchronous 4-bit counter
74163 Synchronous binary counter
74193 Up/down counter
74164 Serial-in/parallel-out shift register
74165 Parallel-in/serial-out shift register

5.4 Decoders and Multiplexers

IC Function
74138 3-to-8 decoder
74139 Dual 2-to-4 decoder
74151 8-to-1 multiplexer
74157 Quad 2-to-1 multiplexer

5.5 Bus Interface and Glue Logic

IC Function
74244 Octal buffer / line driver
74245 Octal bidirectional bus transceiver
74373 Octal transparent latch
74574 Octal D-type FF

6. Pin Numbering Convention

  • DIP packages use counter-clockwise numbering
  • Pin 1 identified by notch or dot
       ________
  1 °|�       |° 14
  2 °|        |° 13
  3 °|        |° 12
  4 °|        |° 11
  5 °|        |° 10
  6 °|        |°  9
  7 °|________|°  8

7. Power and Ground Pins

Package VCC GND
DIP-14 14 7
DIP-16 16 8
DIP-20 20 10

8. Timing Characteristics (General)

Parameter TTL CMOS
Propagation delay 5-15 ns 8-25 ns
Max frequency ~25 MHz ~50+ MHz

9. Interfacing Notes

  • TTL outputs reliably drive TTL inputs
  • CMOS inputs must not float
  • Use 74HCT when interfacing CMOS with TTL signals
  • Decoupling capacitors (0.1 µF) required per IC

10. Typical Retrocomputer Applications

  • Address decoding
  • Chip-select generation
  • Bus buffering
  • Clock gating and control
  • State machines

11. Absolute Maximum Ratings (Summary)

Parameter Rating
VCC -0.5 V to +7.0 V
Input voltage -0.5 V to VCC + 0.5 V
Storage temperature -65 °C to +150 °C

12. References