Interview Question

Senior Process Engineer Interview

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Intel Corporation

Most unexpected: what are the 2 golden rules of an op amp (I’m a mechanical engineer)?

Tags:design, mechatronic, control software, electromechanical
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2 Answers

1

Solution: 1. the output attempts to do whatever is necessary to make the voltage difference between the inputs zero. 2. The inputs draw no current Comments on 1: The voltage gain of a real op-amp is so high that a fraction of a millivolt input will swing the output over its full range. Practically, that amounts to rule1 Comments on 2: The input current is so low (0.08 microamps for the 741, picoamps for an FET-input op-amp) that rule 2 is practically correct.

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1

The positive and negative inputs of an op amp: (1) are the same voltage, and (2) draw no current.

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