Exam-style question
Try this first
Which statement explains why an inverting amplifier can saturate when the input signal amplitude is increased?.
- A.Because the op-amp's input bias current increases with input amplitude.
- B.Because the output voltage will exceed the supply rails, causing the op-amp to saturate.
- C.Because the resistor ratio changes with higher input voltage.
- D.Because the op-amp's bandwidth decreases with higher input amplitude.
Model answer
What a good answer should say
- Because the output voltage will exceed the supply rails, causing the op-amp to saturate.
Explanation
Why this works
Initial state: Input amplitude increases, leading to larger Vout_calc = - (Rf/Rin) * Vin. Step 1: Compute Vout_calc.
Step 2: Compare Vout_calc with supply rails. Step 3: If |Vout_calc| > |V+| or |V−|, the output is limited to the rail, i.e., saturates.
Final state: Output saturates at rail. Conclusion: Saturation occurs because the calculated output exceeds supply rails.
Common mistake
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