Question
What parasitic characteristic causes electrolytic capacitors to be unsuitable for use at RF?
Answer Options
- A) Skin effect
- B) Shunt capacitance
- C) Inductance
- D) Dielectric leakage
Correct Answer: C
Explanation
Electrolytic capacitors are commonly used in power supplies and audio circuits for their very high capacitance values. However, they are fundamentally unsuitable for use at Radio Frequencies (RF), particularly in tuned circuits or decoupling applications above audio frequencies. This unsuitability is due to an internal structural characteristic.
Electrolytic capacitors are constructed by winding two foil strips and a dielectric separator into a compact cylinder. This wound structure introduces a significant amount of Inductance (series parasitic inductance, or ESR). At RF, this parasitic inductance causes the capacitor to become self-resonant at a low frequency and then behave as an inductor above that frequency, completely defeating its intended capacitive purpose.
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