The 74LS series of integrated circuits (ICs) was one of the most popular logic families of transistor-transistor logic (TTL) logic chips. 74LS series is a bipolar, low-power Schottky IC. 74LS40 contain DUAL 4-INPUT NAND BUFFER

74LS40 Features

  • Two Independent NAND Buffer Gates
  • Open Collector Outputs Require External Pull-Up Resistors
  • Fast Switching Times
  • Operating Temperature up to 70°C
  • Standard TTL Switching Voltages

74LS40 Specifications

Supply Voltage4.75 – 5.25Vdc
Maximum Clock Frequency40Mhz
Power Dissipation2mW/gate @100kHz
Minimum Output Current8mA
Propagation Delay10nS
Fan Out (TTL Loads)20

74LS40 Pinout Diagram

74LS40 Pin Description

Pin NoPin NameDescription
1A1NAND Buffer 1 Input 1
2B1 NAND Buffer 1 Input 2
3NCNo Connection
4C1 NAND Buffer 1 Input 3
5D1 NAND Buffer 1 Input 4
6X1 NAND Buffer 1 Output
8X2 NAND Buffer 2 Output
9A2 NAND Buffer 2 Input 1
10B2 NAND Buffer 2 Input 2
11NCNo Connection
12C2 NAND Buffer 2 Input 3
13D2 NAND Buffer 2 Input 4
14VCCPositive Supply

74LS40 Circuit


  • Burglar alarm
  • Freezer warning buzzer

74LS40 Alternative Equivalent

74LS37, 74LS30

Download 74LS40 DUAL 4-INPUT NAND BUFFER Datasheet from the link given below.