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3-to-8 Line Decoder Demultiplexer, TTL Inputs

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The 74AHCT138 is an advanced high speed CMOS device that is designed to be pin compatable with 74LS low power Schottky types. The device accepts a three bit binary weighted address on input pins A0, A1 and A2 and when enab°C will porduce one active low output with the remaing seven being high. There are two active LOW enable inputs 1 and 2, and one active HIGH enable input E3. The disab°C device state results in all outputs being high. The enable state occurs with 1 and 2 asserted low and E3 asserted high. The multiple enable lines allow for the parallel expansion of decoders to create 4-to-16 line versions with no additional parts and 5-to-32 versions with the addition of a single inverter.


  • Memory chip select decoding
  • Demultiplexing
  • Single line peripheral control
  • Allow simple serial bit streams from a microcontroller to control as many peripheral lines as needed.
  • Product Specifications

    Product Parameters

    Number of Gates -
    Family AHCT
    VCC Min (V) 4.5 V
    VCC Maximum Rating 5.5 V
    tpd max @ (1.5V) - ns
    tpd max @ 1.8V (ns) - ns
    tpd max @ 2.5V (ns) - ns
    tpd max @ 3.3V (ns) - ns
    tpd max @ 5.0V (ns) 10.5 ns
    Input/ Output Current -
    Description TTL Inputs, 3-to-8 Line Decoder Demultiplexer
    Output Type Push-Pull

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    Orderable Part Number Buy from Distributor / Contact Sales Request Samples


    Authorized Distributor Quantity Inventory Date Countries/Regions Buy Online
    Digi-Key Electronics 2043 10/4/2022 Europe, Asia, North America Buy Now
    Request Sample


    Authorized Distributor Quantity Inventory Date Countries/Regions Buy Online
    Digi-Key Electronics 2500 10/4/2022 Europe, Asia, North America Buy Now
    Mouser Electronics Inc. 2496 10/4/2022 South America, North America, Asia, Europe, Middle East Buy Now
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    Product Change Notices (PCNs)

    A PCN may only apply to specific orderable part numbers in this datasheet. Please refer to the corresponding PCN to see the exact orderable part number(s) affected.

    PCN # Issue Date Implementation Date Subject
    PCN-2512 2021-04-16 2021-07-16 Qualified Additional Assembly & Test (A/T) Site