Which of the following can provide power gain?
The correct answer is Transistor. A transistor can provide power gain, meaning the output power is greater than the input power. This is the fundamental property that makes transistors useful as amplifiers. A small input signal (voltage or current) controls a larger output signal, with the additional power coming from the power supply. Transistors can provide both voltage gain and current gain, resulting in overall power gain. For amateur radio operators, transistors are essential for amplifying weak received signals, boosting transmitter output power, and providing gain in various circuit stages. This amplification capability is what makes modern solid-state radio equipment possible.
Exam Tip
Only active devices (like transistors) can provide power gain. Passive devices (transformers, reactors, resistors) cannot create power - they can only transfer, store, or dissipate it. Transistors use power from a supply to amplify signals.
Memory Aid
"Transistor = Power gain. Think 'T'ransistor 'T'akes small signal and makes it 'T'en times bigger using supply power. Active device = amplification."
Real-World Application
In your transceiver's RF amplifier, a transistor takes a weak signal from the receiver front-end (perhaps microwatts) and amplifies it to a stronger signal (milliwatts or watts) using power from the supply. The transistor provides power gain by controlling a large current flow with a small input signal. This amplification makes weak signals strong enough to drive speakers or further processing stages.
Key Concepts
Why Other Options Are Wrong
Option A (Transformer): Incorrect. Transformers can provide voltage gain or current gain, but they cannot provide power gain due to conservation of energy. Output power cannot exceed input power in a transformer - they're passive devices.
Option C (Reactor): Incorrect. A reactor typically refers to an inductor used in power systems, which is a passive component that cannot provide power gain. It stores energy but doesn't amplify.
Option D (Resistor): Incorrect. Resistors are passive components that actually dissipate power, reducing signal strength. They cannot provide power gain - they only reduce power through resistance.
题目解析
The correct answer is Transistor. A transistor can provide power gain, meaning the output power is greater than the input power. This is the fundamental property that makes transistors useful as amplifiers. A small input signal (voltage or current) controls a larger output signal, with the additional power coming from the power supply. Transistors can provide both voltage gain and current gain, resulting in overall power gain. For amateur radio operators, transistors are essential for amplifying weak received signals, boosting transmitter output power, and providing gain in various circuit stages. This amplification capability is what makes modern solid-state radio equipment possible.
考试技巧
Only active devices (like transistors) can provide power gain. Passive devices (transformers, reactors, resistors) cannot create power - they can only transfer, store, or dissipate it. Transistors use power from a supply to amplify signals.
记忆口诀
Transistor = Power gain. Think 'T'ransistor 'T'akes small signal and makes it 'T'en times bigger using supply power. Active device = amplification.
实际应用示例
In your transceiver's RF amplifier, a transistor takes a weak signal from the receiver front-end (perhaps microwatts) and amplifies it to a stronger signal (milliwatts or watts) using power from the supply. The transistor provides power gain by controlling a large current flow with a small input signal. This amplification makes weak signals strong enough to drive speakers or further processing stages.
错误选项分析
Option A (Transformer): Incorrect. Transformers can provide voltage gain or current gain, but they cannot provide power gain due to conservation of energy. Output power cannot exceed input power in a transformer - they're passive devices. Option C (Reactor): Incorrect. A reactor typically refers to an inductor used in power systems, which is a passive component that cannot provide power gain. It stores energy but doesn't amplify. Option D (Resistor): Incorrect. Resistors are passive components that actually dissipate power, reducing signal strength. They cannot provide power gain - they only reduce power through resistance.
知识点
Power gain, Transistors, Amplification, Active devices
Verified Content
Question from official FCC Technician Class question pool. Explanation reviewed by licensed amateur radio operators.