Resistor power rating selection (repaired for solvability): A DC bias resistor in a small-signal amplifier is measured to dissipate about 0.18 W under worst-case conditions. According to good design practice (choose the next higher standard wattage so the resistor does not run at its full limit), the minimum power rating for this resistor should be at least ______.

Introduction / Context:Choosing an appropriate resistor power rating is part of reliable circuit design. The rating must exceed the actual worst-case power dissipation so the part does not overheat, drift, or fail prematurely. A common rule is to select the next higher standard rating above the calculated dissipation, typically leaving a margin (for example, running at 50–70% of the rated wattage).

Given Data / Assumptions:

• Measured or calculated worst-case resistor dissipation P_diss ≈ 0.18 W (continuous).
• Ambient conditions are typical; no forced cooling.
• Use standard through-hole ratings such as 1/8 W, 1/4 W, 1/2 W, 1 W, 2 W, etc.

Concept / Approach:First determine the smallest standard rating that is greater than the worst-case dissipation. Then verify that the resulting operating point keeps the resistor comfortably below its limit. Designers often target no more than about 50–70% of the rated wattage in normal service to accommodate tolerances and temperature rise.

Step-by-Step Solution:

Verification / Alternative check:Use P = I^2 * R or P = V^2 / R to recompute the worst case and compare to the data sheet’s derating curves. If the resistor will be in a high-ambient enclosure, consider stepping up to 1/2 W for additional safety margin.

Why Other Options Are Wrong:

Common Pitfalls:Choosing a rating equal to the calculated dissipation with no margin; forgetting that supply tolerance, component tolerance, and ambient temperature can increase real dissipation; ignoring enclosure derating curves.

Final Answer:1/4 W