Digital delay elements – definition of a multitap delay line What best describes a multitap digital delay line implemented with basic logic and passive components?

Digital Electronics Memory and Storage Difficulty: Easy
Choose an option
  • A
    a series of inverter gates with RC circuits between each one
  • B
    a series of inverter gates with RL circuits between each one
  • C
    a series of NAND gates with RC circuits between each one
  • D
    a series of NAND gates with RL circuits between each one

Answer

Correct Answer: a series of inverter gates with RC circuits between each one

Explanation

Introduction / Context:Multitap delay lines are used to create multiple well-defined timing references in digital systems (edge shaping, pulse stretching, time-stamping). Knowing their structure helps when analyzing propagation delay and jitter.

Given Data / Assumptions:

  • The delay line is “digital” and “multitap.”
  • We consider simple gate-level realizations using passives for timing.
  • Taps provide intermediate delayed versions of the same signal.

Concept / Approach:A common discrete implementation chains inverters, each separated by an RC network to create incremental delays. Each node (tap) outputs a progressively delayed replica. Inverters are preferred because they provide restoration, squaring, and predictable propagation; RC networks introduce the controlled time constant. RL versions are uncommon in basic CMOS/TTL design, and using NANDs is unnecessary unless adding gating logic.

Step-by-Step Solution:

Identify the simplest delay element: inverter + RC forms a gate-level delay.Replicate stages and expose intermediate nodes as “taps.”Therefore, the best description is inverters with RC between each.

Verification / Alternative check:Timing chains in many app notes show cascaded inverters with RC shaping or controlled delay cells; ECL/CMOS ICs also implement internal variants of this concept.

Why Other Options Are Wrong:

  • Inverters with RL: RL is not typical for logic-level delay; inductors are bulky and less predictable on PCBs.
  • NAND + RC / NAND + RL: A NAND is not required for pure delay; it adds logic functionality rather than simple timing.

Common Pitfalls:

  • Thinking any multi-gate chain is a “multitap” even without RC timing control.
  • Assuming inductive elements are common in digital delay blocks; they are not.

Final Answer:a series of inverter gates with RC circuits between each one

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