What is an operational amplifier?
The correct answer is A: A high-gain, direct-coupled differential amplifier with very high input impedance and very low output impedance. An operational amplifier (op-amp) is a high-gain, direct-coupled differential amplifier with very high input impedance (typically megohms) and very low output impedance (typically a few ohms).
Op-amps are integrated circuits designed to amplify the difference between two input voltages. They're 'direct-coupled' meaning they can amplify DC signals as well as AC signals. The very high input impedance means they draw minimal current from the signal source, and the very low output impedance means they can drive loads effectively. Op-amps are fundamental building blocks in analog electronics, used in amplifiers, filters, oscillators, and many other circuits. The characteristics described in option A are the defining features of operational amplifiers.
Exam Tip
Op-amp definition = High-gain differential amplifier. Remember: An op-amp is a high-gain, direct-coupled differential amplifier with very high input impedance and very low output impedance.
Memory Aid
"**O**p-amp = **O**utstanding **P**erformance: **H**igh **G**ain, **H**igh **I**nput, **L**ow **O**utput (think 'OP = OPHGHILO')"
Real-World Application
You're building an audio preamplifier using an op-amp. The op-amp's very high input impedance (10 megohms) means it doesn't load down your microphone, and its very low output impedance (10 ohms) means it can drive your headphones effectively. The high gain (100,000 or more) allows you to amplify weak signals, and the differential inputs let you amplify the difference between two signals.
FCC Part 97.3Key Concepts
Why Other Options Are Wrong
Option B: Incorrect. Op-amps are analog amplifiers, not digital audio amplifiers. Their characteristics are determined by internal design, not just external components.
Option C: Incorrect. Op-amps aren't specifically for increasing FM signal output to legal limits. They're general-purpose analog amplifiers used in many applications.
Option D: Incorrect. Op-amps aren't specifically RF amplifiers for UHF and microwave. They're typically used at lower frequencies (audio, DC, low RF).
题目解析
The correct answer is A: A high-gain, direct-coupled differential amplifier with very high input impedance and very low output impedance. An operational amplifier (op-amp) is a high-gain, direct-coupled differential amplifier with very high input impedance (typically megohms) and very low output impedance (typically a few ohms). Op-amps are integrated circuits designed to amplify the difference between two input voltages. They're 'direct-coupled' meaning they can amplify DC signals as well as AC signals. The very high input impedance means they draw minimal current from the signal source, and the very low output impedance means they can drive loads effectively. Op-amps are fundamental building blocks in analog electronics, used in amplifiers, filters, oscillators, and many other circuits. The characteristics described in option A are the defining features of operational amplifiers.
考试技巧
Op-amp definition = High-gain differential amplifier. Remember: An op-amp is a high-gain, direct-coupled differential amplifier with very high input impedance and very low output impedance.
记忆口诀
**O**p-amp = **O**utstanding **P**erformance: **H**igh **G**ain, **H**igh **I**nput, **L**ow **O**utput (think 'OP = OPHGHILO')
实际应用示例
You're building an audio preamplifier using an op-amp. The op-amp's very high input impedance (10 megohms) means it doesn't load down your microphone, and its very low output impedance (10 ohms) means it can drive your headphones effectively. The high gain (100,000 or more) allows you to amplify weak signals, and the differential inputs let you amplify the difference between two signals.
错误选项分析
Option B: Incorrect. Op-amps are analog amplifiers, not digital audio amplifiers. Their characteristics are determined by internal design, not just external components. Option C: Incorrect. Op-amps aren't specifically for increasing FM signal output to legal limits. They're general-purpose analog amplifiers used in many applications. Option D: Incorrect. Op-amps aren't specifically RF amplifiers for UHF and microwave. They're typically used at lower frequencies (audio, DC, low RF).
知识点
Operational amplifier, Differential amplifier, High gain, High input impedance, Low output impedance
Verified Content
Question from official FCC Extra Class question pool. Explanation reviewed by licensed amateur radio operators.