Which of the following components can be used to reduce thermal drift in crystal oscillators?
The correct answer is A: NP0 capacitors. NP0 capacitors (also called C0G capacitors) can be used to reduce thermal drift in crystal oscillators. NP0 capacitors have a very low temperature coefficient (essentially zero temperature coefficient), making them stable over temperature changes.
Crystal oscillators use capacitors in their circuits (for loading, coupling, or tuning). If these capacitors change value with temperature, the oscillator frequency will drift. NP0 (Negative-Positive-Zero) capacitors have a temperature coefficient near zero, so their capacitance doesn't change significantly with temperature. This helps maintain stable oscillator frequency over temperature variations. NP0 capacitors are more expensive than standard capacitors but are essential for temperature-stable oscillators.
Exam Tip
Reduce thermal drift = NP0 capacitors. Remember: NP0 (C0G) capacitors have near-zero temperature coefficient and are used to reduce thermal drift in crystal oscillators.
Memory Aid
"**R**educe **T**hermal **D**rift = **N**P0 **C**apacitors (think 'RTD = NPC' = NP0 Capacitors)"
Real-World Application
You're building a crystal oscillator that needs to stay stable over a wide temperature range. You use NP0 capacitors in the oscillator circuit instead of standard ceramic capacitors. The NP0 capacitors don't change value with temperature, so your oscillator frequency remains stable as the temperature changes, preventing thermal drift.
FCC Part 97.3Key Concepts
Why Other Options Are Wrong
Option B: Incorrect. Toroidal inductors are used for their magnetic properties and low radiation, but they don't specifically reduce thermal drift in crystal oscillators.
Option C: Incorrect. Wirewound resistors are stable resistors, but they don't reduce thermal drift in crystal oscillators. The drift comes from capacitors, not resistors.
Option D: Incorrect. Non-inductive resistors are used to avoid inductance, but they don't reduce thermal drift in crystal oscillators.
题目解析
The correct answer is A: NP0 capacitors. NP0 capacitors (also called C0G capacitors) can be used to reduce thermal drift in crystal oscillators. NP0 capacitors have a very low temperature coefficient (essentially zero temperature coefficient), making them stable over temperature changes. Crystal oscillators use capacitors in their circuits (for loading, coupling, or tuning). If these capacitors change value with temperature, the oscillator frequency will drift. NP0 (Negative-Positive-Zero) capacitors have a temperature coefficient near zero, so their capacitance doesn't change significantly with temperature. This helps maintain stable oscillator frequency over temperature variations. NP0 capacitors are more expensive than standard capacitors but are essential for temperature-stable oscillators.
考试技巧
Reduce thermal drift = NP0 capacitors. Remember: NP0 (C0G) capacitors have near-zero temperature coefficient and are used to reduce thermal drift in crystal oscillators.
记忆口诀
**R**educe **T**hermal **D**rift = **N**P0 **C**apacitors (think 'RTD = NPC' = NP0 Capacitors)
实际应用示例
You're building a crystal oscillator that needs to stay stable over a wide temperature range. You use NP0 capacitors in the oscillator circuit instead of standard ceramic capacitors. The NP0 capacitors don't change value with temperature, so your oscillator frequency remains stable as the temperature changes, preventing thermal drift.
错误选项分析
Option B: Incorrect. Toroidal inductors are used for their magnetic properties and low radiation, but they don't specifically reduce thermal drift in crystal oscillators. Option C: Incorrect. Wirewound resistors are stable resistors, but they don't reduce thermal drift in crystal oscillators. The drift comes from capacitors, not resistors. Option D: Incorrect. Non-inductive resistors are used to avoid inductance, but they don't reduce thermal drift in crystal oscillators.
知识点
NP0 capacitors, Thermal drift, Crystal oscillators, Temperature stability
Verified Content
Question from official FCC Extra Class question pool. Explanation reviewed by licensed amateur radio operators.