Question
What is a common use for point-contact diodes?
Answer Options
- A) As a constant current source
- B) As a constant voltage source
- C) As an RF detector
- D) As a high-voltage rectifier
Correct Answer: C
Explanation
A point-contact diode is one of the oldest forms of semiconductor rectifiers, using a fine metal whisker pressed against a semiconductor crystal. Like the Schottky diode, this structure is characterized by very low junction capacitance and fast switching speed. However, they are generally fragile and have low power handling capability.
Because of their fast response and low capacitance, a common use for point-contact diodes is as an RF detector in crystal radio sets and low-power measurement equipment. They are very effective at rectifying or demodulating high-frequency radio waves, where bulkier, slower junction diodes would fail due to charge storage effects.
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