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Question 302

What is used to control the attenuation of RF signals by a PIN diode?

  1. Forward DC bias currentBonne réponse
  2. A variable RF reference voltage
  3. Reverse voltage larger than the RF signal
  4. Capacitance of an RF coupling capacitor

Explication

At radio frequencies a forward-biased PIN diode behaves as a resistor whose value is set by the charge stored in its intrinsic layer, and that charge is set by the DC forward current, so varying the bias current varies attenuation smoothly and without distorting the signal. Reverse voltage only switches the diode off, and coupling capacitance is not a control at all.

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