Question
What is the primary cause of loss in film capacitors at RF?
Answer Options
- A) Inductance
- B) Dielectric loss
- C) Self-discharge
- D) Skin effect
Correct Answer: B
Explanation
All capacitors exhibit some level of internal energy dissipation (loss), which is usually modeled as an Equivalent Series Resistance (ESR). This loss prevents the capacitor from being a perfect energy storage device. In high-quality film capacitors used at RF, two main causes of loss are parasitic resistance in the leads/foils and losses within the insulating material itself.
The primary cause of loss in film capacitors at RF is Dielectric loss. This is the energy absorbed and dissipated as heat by the insulating material (the dielectric) sandwiched between the capacitor’s conductive plates. Dielectric loss increases with frequency and can significantly degrade the Q and performance of the capacitor in high-frequency tuned circuits.
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