TTL JK flip-flop (74LS76) datasheet practice: What is the required setup time (ts) for valid J/K data relative to the active clock edge on a 74LS76 device?

Introduction / Context:
Setup time (ts) is a fundamental timing parameter for flip-flops. It specifies how long the input data must be stable before the active clock edge to ensure the internal latches sample correctly. For TTL JK devices such as the 74LS76, honoring ts prevents metastability and incorrect toggling.

Given Data / Assumptions:

• Target device: 74LS76 (JK flip-flop, TTL, Low-Power Schottky family).
• We assume standard TTL supply (5 V) and typical datasheet conditions.
• We need the recommended setup time ts for J or K relative to the active clock edge.

Concept / Approach:
Setup time must be met so that the input logic levels are reliably captured by the clocked storage elements. Violating ts can lead to unpredictable outputs or oscillations at Q. Datasheets provide a minimum ts that designers should meet or exceed in timing closure analysis.

Step-by-Step Solution:
Identify timing parameter: ts (data stable before clock edge).Consult typical LS-family values for JK flip-flops like 74LS76.Adopt the commonly specified requirement: ts ≈ 20 ns for reliable operation.

Verification / Alternative check:
Designers often include margin beyond ts to account for temperature, voltage, and process variations, ensuring robust timing even under worst-case conditions.

Why Other Options Are Wrong:
5 ns, 10 ns: unrealistically short for LS TTL JK timing at 5 V.40 ns: overly conservative compared to typical datasheet requirements.15 ns: closer, but still below the common 20 ns figure used for safe design.

Common Pitfalls:
Confusing setup with hold time; both must be met. Also, assuming the same ts across all logic families can cause violations; always check the actual part’s datasheet.

Final Answer:
20 ns