Which decoder type selects exactly one of sixteen output lines as active, based solely on the binary value of a 4-bit input word?

Introduction / Context:
Decoders translate binary codes into one-hot outputs. A classic example is using a 4-bit input to activate one of sixteen lines, a building block for address decoding and device selection in digital systems. This is often referred to as a 4-to-16 or binary-to-hexadecimal decoder because sixteen distinct outputs correspond to the sixteen hexadecimal symbols (0–F).

Given Data / Assumptions:

• Input width = 4 bits.
• Output count = 16 lines.
• Exactly one output should be asserted for each input pattern.

Concept / Approach:
A 4-to-16 decoder maps the 4-bit input to a one-hot 16-bit output. For input N (0..15), only YN is active. This functionality is commonly used for memory address line decoding, selecting registers, or enabling peripherals where only one device should respond to a given code.

Step-by-Step Solution:
Let input be A3..A0 and outputs Y0..Y15.For input 0101 (decimal 5), assert Y5; all others deasserted.Repeat for all 16 combinations to cover 0x0 through 0xF.Thus, a binary-to-hexadecimal (4-to-16) decoder is required.

Verification / Alternative check:
Commercial parts like the 74HC154 provide 4-to-16 decoding with active-low outputs and enable pins, matching the described behavior and confirming the mapping from 4-bit binary to sixteen one-hot outputs.

Why Other Options Are Wrong:

• Hexadecimal (alone): Not a functional description.
• Dual octal outputs: Suggests two 3-to-8 decoders, not one 4-to-16.
• Hexadecimal-to-binary: The opposite direction of decoding.
• 4-to-8 with enable: Only eight outputs, not sixteen.

Common Pitfalls:

• Overlooking active-low output conventions that invert logic levels.
• Forgetting enable pins must be set correctly for decoding to operate.

Final Answer:
binary-to-hexadecimal