74HCT00 — Quad 2-Input NAND Gate with TTL-Compatible Inputs

Overview

The 74HCT00 (SN74HCT00) is a high-speed silicon-gate CMOS integrated circuit containing four independent 2-input NAND logic gates. It provides identical logical functionality and pinout to the standard 74HC00 and legacy 74LS00, but is fabricated with TTL-compatible input switching thresholds.

Operating from a standard $+5.0\text{V}$ power rail, the 74HCT00 recognizes any input above $V_{IH} \ge 2.0\text{V}$ as a valid logic HIGH (and below $V_{IL} \le 0.8\text{V}$ as a logic LOW), while driving full rail-to-rail CMOS outputs ( $0\text{V}$ to $5\text{V}$ ). This makes the 74HCT00 an essential interface element for connecting 3.3V microcontroller outputs (ESP32, Raspberry Pi, ARM Cortex) or classic 74LS TTL chips directly to 5V CMOS logic gates.

Quick reference


Supply Voltage (`VCC`)	4.5 V to 5.5 V DC (5.0 V nominal)
Logic Family	TTL-Compatible High-Speed CMOS (74HCT)
Gate Count	4 Independent 2-Input NAND Gates
Input Thresholds	$V_{IH} \ge 2.0\text{ V}$ , $V_{IL} \le 0.8\text{ V}$ (Direct 3.3V / TTL compatibility)
Logic Function	$Y = \overline{A \cdot B}$
Propagation Delay ( $t_{pd}$ )	$10\text{ ns}$ typ ( $20\text{ ns}$ max) at $V_{CC} = 4.5\text{V}$
Output Drive Current	$\pm 4.0\text{ mA}$ at $V_{CC} = 4.5\text{V}$
Package Options	14-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│74HCT00│11 4Y
          2B 5│       │10 3B
          2Y 6│       │9  3A
         GND 7│       │8  3Y
             └───────┘

Pin	Name	Type	Description
1, 2	`1A`, `1B`	Digital Input	Gate 1 Data Inputs (TTL/3.3V compatible)
3	`1Y`	Digital Output	Gate 1 NAND Output ( $1Y = \overline{1A \cdot 1B}$ )
4, 5	`2A`, `2B`	Digital Input	Gate 2 Data Inputs
6	`2Y`	Digital Output	Gate 2 NAND Output ( $2Y = \overline{2A \cdot 2B}$ )
7	`GND`	Power	Ground reference (0 V)
8	`3Y`	Digital Output	Gate 3 NAND Output ( $3Y = \overline{3A \cdot 3B}$ )
9, 10	`3A`, `3B`	Digital Input	Gate 3 Data Inputs
11	`4Y`	Digital Output	Gate 4 NAND Output ( $4Y = \overline{4A \cdot 4B}$ )
12, 13	`4A`, `4B`	Digital Input	Gate 4 Data Inputs
14	`VCC`	Power	Supply voltage (+4.5 V to +5.5 V DC)

Function Table

Input A	Input B	Output Y ( $\overline{A \cdot B}$ )
Low ( $L \le 0.8\text{V}$ )	Low ( $L \le 0.8\text{V}$ )	High ( $H \ge 4.4\text{V}$ )
Low ( $L \le 0.8\text{V}$ )	High ( $H \ge 2.0\text{V}$ )	High ( $H \ge 4.4\text{V}$ )
High ( $H \ge 2.0\text{V}$ )	Low ( $L \le 0.8\text{V}$ )	High ( $H \ge 4.4\text{V}$ )
High ( $H \ge 2.0\text{V}$ )	High ( $H \ge 2.0\text{V}$ )	Low ( $L \le 0.1\text{V}$ )

Specifications

Parameter	Symbol	Min	Typ	Max	Unit	Conditions
Supply Voltage	$V_{CC}$	4.5	5.0	5.5	V	Standard HCT range
High-Level Input Voltage	$V_{IH}$	2.0	—	—	V	$V_{CC} = 4.5\text{V} \dots 5.5\text{V}$
Low-Level Input Voltage	$V_{IL}$	—	—	0.8	V	$V_{CC} = 4.5\text{V} \dots 5.5\text{V}$
High-Level Output Voltage	$V_{OH}$	4.4	4.5	—	V	$V_{CC} = 4.5\text{V}, I_{OH} = -20\ \mu\text{A}$
High-Level Output Voltage (Load)	$V_{OH}$	3.84	4.32	—	V	$V_{CC} = 4.5\text{V}, I_{OH} = -4.0\text{ mA}$
Low-Level Output Voltage	$V_{OL}$	—	0.0	0.1	V	$V_{CC} = 4.5\text{V}, I_{OL} = 20\ \mu\text{A}$
Low-Level Output Voltage (Load)	$V_{OL}$	—	0.17	0.33	V	$V_{CC} = 4.5\text{V}, I_{OL} = 4.0\text{ mA}$
Propagation Delay	$t_{PLH}, t_{PHL}$	—	10	20	ns	$V_{CC} = 4.5\text{V}, C_L = 50\text{ pF}$
Quiescent Current	$I_{CC}$	—	—	2.0	µA	$V_{IN} = V_{CC}\text{ or GND}$

Common mistakes

Powering below 4.5V: Standard 74HCT logic requires a regulated $5\text{V} \pm 10\%$ rail ( $4.5\text{V} \dots 5.5\text{V}$ ). It cannot operate reliably at $3.3\text{V}$ or $2.0\text{V}$ (use 74HC00 or 74LVC00 for low-voltage supplies).
Leaving unused gate inputs floating: Unconnected CMOS inputs float, generating internal shoot-through currents and sporadic output toggling. Tie unused input pins to $V_{CC}$ or $GND$ .
Confusing 74HC00 with 74HCT00 for 3.3V logic translation: A standard 74HC00 powered by 5V requires $V_{IH} \ge 3.15\text{V}$ , which provides negligible margin for 3.3V signals. Always specify 74HCT00 when driving from 3.3V microcontrollers into 5V logic.

Notes

Pin-Compatible Replacements: 74HC00, 74LS00, 74ALS00, SN74HCT00N, CD74HCT00.