Exam-style question
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Explain why a real op‑amp may saturate at its supply rails and how this limitation can be mitigated in a design.
Model answer
What a good answer should say
- A real op‑amp can only output voltages within a few volts of its supply rails; if the required output exceeds this range the output saturates at the rail voltage.
- This occurs because the internal transistors cannot drive the output beyond the supply limits.
- Designers mitigate this by using higher supply voltages, rail‑to‑rail output stages, or by adding external buffering stages to provide the necessary headroom.
Explanation
Why this works
This question assesses the student’s understanding of output voltage limits (saturation) in real op‑amps and the practical design strategies used to overcome this limitation, such as rail‑to‑rail outputs or higher supply voltages.
Common mistake
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