Ripple counter speed limitation In an asynchronous (ripple) counter, the maximum speed is limited primarily by the propagation delay of which elements?

Introduction / Context:
Ripple counters clock each successive flip-flop with the output of the previous stage. This creates a chain of sequential delays. Understanding which delays dominate sets expectations for maximum count frequency and informs when a synchronous counter is necessary.

Given Data / Assumptions:

• Asynchronous topology: stage n+1 is clocked by stage n's output.
• Flip-flops have a finite clock-to-Q propagation delay.
• Minimal combinational gating lies in the clock path for simple ripple counters.

Concept / Approach:
The worst-case time for the most significant stage to settle equals the sum of the per-stage clock-to-Q delays of all preceding flip-flops. Thus, the flip-flop chain's propagation delays limit speed. External gates may appear in decoding, but they are not in the internal ripple clock path for basic counters.

Step-by-Step Solution:

Verification / Alternative check:
Measure a ripple counter's outputs on a scope: higher-order bits lag the low-order bits by multiples of t_pd(ff), plainly showing the cumulative flip-flop delays.

Why Other Options Are Wrong:

• All flip-flops and gates / the flip-flops only with gates / only gates: In basic ripple counters, the critical path is the flip-flop chain, not external gating.

Common Pitfalls:
Assuming synchronous timing or ignoring accumulated delay when decoding multiple bits immediately after a transition (can cause glitches).

Final Answer:
each flip-flop