Question
Why should wire-wound resistors not be used in RF circuits?
Answer Options
- A) The resistor’s tolerance value would not be adequate
- B) The resistor’s inductance could make circuit performance unpredictable
- C) The resistor could overheat
- D) The resistor’s internal capacitance would detune the circuit
Correct Answer: B
Explanation
Wire-wound resistors are commonly used in high-power applications (like power supplies) because they can dissipate significant heat. However, they are generally constructed by winding a resistive wire around a form. This coiled construction creates a high degree of inductance.
At Radio Frequencies (RF), this unintended inductance becomes a dominant factor, introducing significant reactive impedance into the circuit. This makes the resistor behave like an RL network, meaning the resistor’s inductance could make circuit performance unpredictable, leading to detuning of resonant circuits or poor filter performance. Non-inductive resistors (like carbon composition) are preferred for RF circuits.
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