Overview

The 74HC08 (SN74HC08) is a quad 2-input AND gate IC manufactured using high-speed silicon-gate CMOS technology. Containing four independent 2-input AND gates in a 14-pin DIP/SOIC package, it performs the Boolean function Y=A⋅BY = A \cdot B or Y=A‾+B‾‾Y = \overline{\overline{A} + \overline{B}} in positive logic.

Operating from a wide supply voltage range of 2.0V to 6.0V DC, it combines low power CMOS consumption with high-speed switching speeds comparable to Low-Power Schottky TTL (LS-TTL). It is a staple component in digital logic kits, signal gating networks, enable/disable switches, and safety interlock systems.

Quick reference

Supply Voltage (VCC)2.0 V to 6.0 V DC
Logic FamilyHigh-Speed CMOS (74HC) / TTL Compatible (74HCT)
Independent Gates4 (Quad 2-Input AND)
Propagation Delay7 ns7\text{ ns} typical at VCC=5.0VVCC = 5.0\text{V}
Output Drive Current±5.2 mA\pm 5.2\text{ mA} at VCC=4.5VVCC = 4.5\text{V}
Package14-pin DIP / SOIC-14 / TSSOP-14

Pinout (DIP-14 Package)

text
             ┌───┴───┐
          1A 1│ 1   14│ VCC
          1B 2│       │13 4B
          1Y 3│       │12 4A
          2A 4│ 74HC08│11 4Y
          2B 5│       │10 3B
          2Y 6│       │9  3A
         GND 7│       │8  3Y
             └───────┘
PinNameDescription
11AGate 1 Input A
21BGate 1 Input B
31YGate 1 Output (1Y=1A⋅1B1Y = 1A \cdot 1B)
42AGate 2 Input A
52BGate 2 Input B
62YGate 2 Output (2Y=2A⋅2B2Y = 2A \cdot 2B)
7GNDGround reference (0 V)
83YGate 3 Output (3Y=3A⋅3B3Y = 3A \cdot 3B)
93AGate 3 Input A
103BGate 3 Input B
114YGate 4 Output (4Y=4A⋅4B4Y = 4A \cdot 4B)
124AGate 4 Input A
134BGate 4 Input B
14VCCPower supply voltage (+2.0V to +6.0V DC)

Function & Truth Table (Per Gate)

Input AInput BOutput Y
Low (LL)Low (LL)Low (LL)
Low (LL)High (HH)Low (LL)
High (HH)Low (LL)Low (LL)
High (HH)High (HH)High (HH)

Specifications

ParameterSymbolMinTypMaxUnitConditions
Supply VoltageVCCV_{CC}2.05.06.0VDC
High-Level Input VoltageVIHV_{IH}3.15——VVCC=4.5VV_{CC} = 4.5\text{V}
Low-Level Input VoltageVILV_{IL}——1.35VVCC=4.5VV_{CC} = 4.5\text{V}
Propagation Delay (A,B→YA,B \rightarrow Y)tPDt_{PD}—715nsVCC=4.5V,CL=50pFV_{CC} = 4.5\text{V}, C_L = 50\text{pF}
Output Drive CurrentIOUTI_{OUT}——±5.2\pm 5.2mAVCC=4.5VV_{CC} = 4.5\text{V}
Quiescent Supply CurrentICCI_{CC}——2.0µAVIN=VCC or GNDV_{IN} = V_{CC}\text{ or GND}

Typical Applications

Signal Gate / Pulse Enable Control

Passing a PWM clock signal to a motor driver or buzzer only when a control ENABLE pin is HIGH.

text
  Clock Signal ────────► [Pin 1: 1A]
                          74HC08 ───► [Pin 3: 1Y] ───► Gated Clock Out (Active when ENABLE is High)
  Enable Control ──────► [Pin 2: 1B]

Common mistakes

  • Leaving inputs of unused AND gates floating: Unused CMOS gate inputs (e.g. pins 4, 5, 9, 10, 12, 13) must be tied to VCCV_{CC} or GND. Floating CMOS inputs drift into linear operating regions, causing high supply current draw and cross-talk noise.
  • Driving 74HC08 inputs with 3.3V logic when powered from 5V: When powered from VCC=5VV_{CC} = 5\text{V}, the 74HC08 requires VIH≥3.15VV_{IH} \ge 3.15\text{V}. A 3.3V GPIO output is right on the noise margin threshold. Use the 74HCT08 variant (VIH≥2.0VV_{IH} \ge 2.0\text{V}) for 3.3V to 5V TTL level compatibility.

Notes

  • 74HC08 vs 74HC00 vs 74HC11: 74HC08 contains quad 2-input AND gates; 74HC00 contains quad 2-input NAND gates; 74HC11 contains triple 3-input AND gates.

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