74LS139 2 to 4 Decoder/Demultiplexer


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. 74LS139 comprises two individual two-line to four-line decoders in a single package. The active-low enable input can be used as a data line in demultiplexing applications.

74LS139 Features

  • Two Independent Two-of-Four Decoders Based Upon the Select Inputs
  • Inputs Clamped with Schottky Diodes
  • Designed for Memory Decoders and Data Transmission Systems
  • Operating Temperature up to 70°C
  • Standard TTL Switching Voltages

74LS139 Specifications

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

74LS139 Pinout Diagram

74LS139 Pin Description

Pin NoPin NameDescription
1EaDecoder A Enable Pin
2A0aInput 0 of Decoder A
3A1aInput 1 of Decoder A
4O0aOutput 0 of Decoder A
5O1aOutput 1 of Decoder A
6O2aOutput 2 of Decoder A
7O3aOutput 3 of Decoder A
8GNDGround Pin
9O3bOutput 3 of Decoder B
10O2bOutput 2 of Decoder B
11O1bOutput 1 of Decoder B
12O0bOutput 0 of Decoder B
13A1bInput 1 of Decoder B
14A0bInput 0 of Decoder B
15EbDecoder B Enable Pin
16VCCPositive Supply

74LS139 Circuit


  • It is used in code conversion.  i.e analog to digital conversion in the analog decoder.
  • It may also be used for data distribution.
  • In a high-performance memory system, this decoding can be used to minimize the effect of system decoding.

74LS139 Alternative Equivalent


Download 74LS139 2 to 4 Decoder/Demultiplexer Datasheet from the link given below.