Deep Dive: E7G08
The correct answer is D: It does not vary with frequency. For an ideal operational amplifier, the gain does not vary with frequency - it's constant at all frequencies. This is a characteristic of the ideal op-amp model used for circuit analysis. In reality, op-amps have frequency-dependent gain due to internal capacitances and other effects, but the ideal op-amp model assumes infinite gain that's constant with frequency. This simplifies circuit analysis. Real op-amps have a gain that decreases with frequency (due to the gain-bandwidth product), but the ideal model assumes constant infinite gain. The ideal op-amp also assumes infinite input impedance, zero output impedance, and infinite bandwidth - all frequency-independent.
Why Other Answers Are Wrong
Option A: Incorrect. Ideal op-amp gain doesn't increase with frequency. It's constant (infinite) at all frequencies. Option B: Incorrect. Ideal op-amp gain doesn't decrease linearly with frequency. Real op-amps do, but ideal ones don't. Option C: Incorrect. Ideal op-amp gain doesn't decrease logarithmically. Real op-amps have frequency-dependent gain, but ideal ones have constant infinite gain.
Exam Tip
Ideal op-amp gain = Constant with frequency. Remember: An ideal op-amp has constant (infinite) gain that doesn't vary with frequency. Real op-amps have frequency-dependent gain, but the ideal model assumes constant gain.
Memory Aid
**I**deal **O**p-amp = **I**nfinite **C**onstant (think 'IO = IC' = Infinite Constant, doesn't vary with frequency)
Real-World Example
When analyzing an op-amp circuit using the ideal op-amp model, you assume the gain is infinite and constant at all frequencies. This simplifies calculations. In reality, your op-amp might have a gain-bandwidth product of 1 MHz, meaning gain decreases with frequency, but for initial circuit design, the ideal model (constant infinite gain) is useful.
Source & Coverage
Question Pool: 2024-2028 Question Pool
Subelement: E7G
Reference: FCC Part 97.3
Key Concepts
Verified Content
Question from the official FCC Extra Class pool. Explanation reviewed by licensed amateur radio operators and mapped to the E7G topic.