What absolute voltage gain can be expected from the circuit in Figure E7-3 when R1 is 3,300 ohms and RF is 47 kilohms?

Q: What absolute voltage gain can be expected from the circuit in Figure E7-3 when R1 is 3,300 ohms and RF is 47 kilohms?

The correct answer is B: 14. The correct answer is B: 14. For the inverting op-amp circuit in Figure E7-3, the absolute voltage gain is calculated as RF / R1 (the absolute value, ignoring the negative sign for inversion). With R1 = 3,300 ohms and RF = 47 kilohms (47,000 ohms): Gain = RF / R1 = 47,000 / 3,300 = 14.24, which rounds to approximately 14. The absolute gain is 14, meaning the output amplitude is 14 times the input amplitude (but inverted). This is a straightforward calculation: divide the feedback resistor by the input resistor.

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Deep Dive: E7G11

The correct answer is B: 14. For the inverting op-amp circuit in Figure E7-3, the absolute voltage gain is calculated as RF / R1 (the absolute value, ignoring the negative sign for inversion). With R1 = 3,300 ohms and RF = 47 kilohms (47,000 ohms): Gain = RF / R1 = 47,000 / 3,300 = 14.24, which rounds to approximately 14. The absolute gain is 14, meaning the output amplitude is 14 times the input amplitude (but inverted). This is a straightforward calculation: divide the feedback resistor by the input resistor.

Why Other Answers Are Wrong

Option A: Incorrect. 28 would be approximately 2 × 14, suggesting a calculation error or misreading of the resistor values. Option C: Incorrect. 7 would be approximately half of 14, suggesting a calculation error. Option D: Incorrect. 0.07 would be R1 / RF (3,300 / 47,000), which is the inverse of the correct formula.

Exam Tip

Absolute op-amp gain = RF / R1. Remember: For an inverting op-amp, absolute gain = RF / R1. With RF = 47kΩ and R1 = 3.3kΩ, gain = 47,000 / 3,300 ≈ 14.

Memory Aid

**A**bsolute **G**ain = **R**F / **R**1 (think 'AG = RF/R1' = Absolute Gain = RF divided by R1)

Real-World Example

You're designing an inverting amplifier with R1 = 3.3kΩ and RF = 47kΩ. The absolute voltage gain is 47,000 / 3,300 = 14.24, approximately 14. This means the output amplitude will be 14 times the input amplitude (but inverted in polarity).

Source & Coverage

Question Pool: 2024-2028 Question Pool

Subelement: E7G

Reference: FCC Part 97.3

Key Concepts

Op-amp gain Inverting amplifier Absolute gain RF / R1

Official Pool Source

Question text and answer key are synchronized with the current NCVEC Extra Class pool and mapped to the E7G topic.