The 74HC42N is a BCD-to-decimal decoder IC that converts a 4-bit Binary-Coded Decimal (BCD) input into one of 10 mutually exclusive active-low outputs.

It is part of the 74HC high-speed CMOS logic family and is pin-compatible with corresponding low-power Schottky TTL devices. The IC is suitable for digital decoding, address selection, control circuits, demultiplexing, and educational electronics projects.

Key Features

• BCD-to-decimal decoder
• 4 active-high BCD inputs
• 10 active-low outputs
• Mutually exclusive outputs
• Only one output is selected for each valid BCD input
• Outputs remain HIGH for invalid BCD input codes above 9
• Supports 1-of-8 demultiplexing
• Standard logic output capability
• 16-pin package
• Wide 2V to 6V supply voltage range
• 74HC high-speed CMOS logic family

How It Works

The 74HC42 accepts a 4-bit BCD input representing decimal values from 0 to 9.

For each valid BCD input, the corresponding decimal output becomes LOW, while all other outputs remain HIGH.

For binary input codes from 1010 to 1111 (10–15), all outputs remain HIGH.

1-of-8 Demultiplexer Operation

The IC can also be configured for 1-of-8 demultiplexing applications.

The most significant input can provide an inhibit/control function, while the remaining inputs determine the selected output. This allows the device to be used for signal routing and selection in digital logic circuits.

Technical Specifications

Applications

Suitable for:

• BCD-to-decimal conversion
• Digital decoding circuits
• Address decoding
• Output selection
• Control systems
• Digital displays
• Demultiplexing
• Logic circuit design
• Microcontroller interfacing
• Breadboard experiments
• Educational electronics
• Digital logic projects

The 74HC42N BCD-to-Decimal Decoder provides a simple and reliable way to convert a 4-bit BCD value into one of ten individually selectable active-low outputs.