Slew rate calculation — check the claim: It takes 4 µs for an op-amp output to transition from −14 V to +14 V (a 28 V step). Is the slew rate 3.5 V/µs as stated, or a different value?
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ACorrect
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BIncorrect
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COnly correct for peak values, not RMS
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DOnly correct with capacitive loading
Answer
Correct Answer: Incorrect
Explanation
Introduction / Context:Slew rate (SR) is the maximum rate of change of an op-amp’s output voltage and sets a hard limit on how fast the output can swing. It is crucial for large-signal performance, preventing distortion in fast waveforms and step responses. This problem checks a numeric SR claim using simple arithmetic.
Given Data / Assumptions:
- Voltage change ΔV = +14 − (−14) = 28 V.
- Transition time Δt = 4 µs.
- Definition: SR = ΔV / Δt (in V/µs).
Concept / Approach:Compute SR = 28 V / 4 µs = 7 V/µs. The statement “3.5 V/µs” is exactly half of the correct value and therefore incorrect. No RMS versus peak distinction applies here; slew rate is a time-derivative limit on the instantaneous output voltage, determined by internal current limiting and compensation capacitances.
Step-by-Step Solution:
1) Calculate ΔV = 28 V.2) Use SR = ΔV / Δt = 28 / 4 = 7 V/µs.3) Compare with the claim 3.5 V/µs → mismatch.4) Conclude the claim is false; correct SR is 7 V/µs.Verification / Alternative check:If the amplifier had a 3.5 V/µs limit, the same 28 V step would require 8 µs, not 4 µs. This cross-check confirms that 4 µs implies 7 V/µs.
Why Other Options Are Wrong:
- Correct: Not correct, as the computed value is 7 V/µs.
- Only correct for peak values, not RMS: Slew rate is not an RMS concept.
- Only correct with capacitive loading: External load may influence behavior but does not alter the basic ΔV/Δt calculation given.
Common Pitfalls:Confusing full-swing step with half-swing; mixing bandwidth limits (small-signal) with slew-rate (large-signal) limitations.
Final Answer:Incorrect