This question was asked inGPSC Deputy Executive Engineer (Electrical) Class-2 Master Paper 2026Question 67 of 195 published · Gujarat Public Service CommissionOpen paper
Q67EasySequential Circuits

Consider the following statements regarding Counters:
1. Asynchronous counters experience cumulative propagation delay due to ripple effect, limiting their operating speed in high-frequency applications.
2. All synchronous counters are free from decoding glitches and hazards under all operating conditions.
3. Synchronous counters eliminate ripple delay by clocking all flip-flops simultaneously, thereby improving speed and reliability.
Which of the above statements is/are correct?

Answer & step-by-step solution
Correct answer: C. 1 and 3 only
Quick explanation

Asynchronous or ripple counters clock each stage from the previous stage, so propagation delays accumulate. Synchronous counters clock all flip-flops together and are therefore faster, but combinational decoding can still exhibit hazards/glitches depending on implementation. Key relation: Ripple delay roughly accumulates with number of stages.

Exam focus: Synchronous eliminates ripple-clock delay, not every possible logic hazard. Common trap: Synchronous does not mean glitch-proof.

Statement-wise Verification

  • Statement 1 - Correct.
    Asynchronous counters experience cumulative propagation delay due to ripple effect, limiting their operating speed in high-frequency applications.
    Asynchronous or ripple counters clock each stage from the previous stage, so propagation delays accumulate.
  • Statement 2 - Incorrect.
    All synchronous counters are free from decoding glitches and hazards under all operating conditions.
    Synchronous clocking removes ripple delay but does not guarantee hazard-free decoding logic
  • Statement 3 - Correct.
    Synchronous counters eliminate ripple delay by clocking all flip-flops simultaneously, thereby improving speed and reliability.
    Synchronous counters clock all flip-flops together and are therefore faster

Core Concept

Asynchronous or ripple counters clock each stage from the previous stage, so propagation delays accumulate. Synchronous counters clock all flip-flops together and are therefore faster, but combinational decoding can still exhibit hazards/glitches depending on implementation.

Formula / Key Relationship

Ripple delay roughly accumulates with number of stages.

Why the Other Options Are Wrong

Option A is incorrect because it includes incorrect statement(s) 2 and omits correct statement(s) 3. Option B is incorrect because it includes incorrect statement(s) 2 and omits correct statement(s) 1. Option D is incorrect because it includes incorrect statement(s) 2.

Exam Shortcut / Approach

Synchronous eliminates ripple-clock delay, not every possible logic hazard.

Common Mistake

Synchronous does not mean glitch-proof.

Quick Revision

Synchronous and Asynchronous Counters is linked with Counters, Sequential Logic and Digital Electronics. Synchronous eliminates ripple-clock delay, not every possible logic hazard.

Exam tipSynchronous eliminates ripple-clock delay, not every possible logic hazard.
Verified · SRO editorial desk Report
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