PN junctions and diodes

When a sinusoidal AC signal is applied to a half-wave rectifier made of one diode and a resistor, what is the output?

  1. AThe AC signal passes through unchanged
  2. BThe negative half-cycles are also flipped and output as positive
  3. COnly one half-cycle, either positive or negative, is output
Show answer and explanation

Answer: C. Only one half-cycle, either positive or negative, is output

In a half-wave rectifier, current flows only during the half-cycle in which the diode is forward biased, and the other half-cycle is blocked. The output therefore consists of only one half of each cycle. To use both halves, a full-wave rectifier such as a bridge rectifier is used.

  • A. The diode blocks reverse current, so the AC does not pass unchanged.
  • B. Flipping the negative half-cycles is what a full-wave rectifier does.
  • C. Correct. Only one half-cycle is output.
Practice this topic Back to topic

More PN junctions and diodes questions

  1. When an LED is connected to a power supply to light it, what is the main purpose of a resistor in series with the LED?
  2. What is the main purpose of placing a capacitor in parallel with the output of a rectifier?
  3. How does the forward voltage of a silicon diode carrying a constant current change as the temperature rises?
  4. For an ideal diode (ideality factor n = 1) at room temperature, roughly how much must the forward voltage increase to raise the forward current tenfold?
  5. Which expression gives the depletion (junction) capacitance C of a reverse-biased PN junction in terms of junction area A, depletion width W and semiconductor permittivity ε?