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P-N Junction Diode Characteristics Experiment

Oct 12, 2024

P-N Junction Diode Characteristics Experiment

Overview

  • Objective: Observe the forward bias and reverse bias characteristics of a p-n junction diode.

Components and Connections

  • Diode: Has two terminals - p-type (anode) and n-type (cathode).
  • Resistor: 1 kΩ resistor connected in series with the diode.
  • RPS (Regulated Power Supply): Positive and Negative terminals to control voltage.
  • Voltmeter: Measures voltage across the diode.
  • Ammeter: Measures current passing through the diode.

Circuit Connection (Forward Bias)

  1. Connect 1 kΩ resistor in series with the diode.
  2. RPS positive terminal connected to the first terminal of resistor.
  3. RPS negative terminal connected to the ground.
  4. Voltmeter positive connected to the diode's p-type.
  5. Voltmeter negative connected to the diode's n-type.
  6. Ammeter positive connected to diode's n-type.
  7. Ammeter negative connected to ground.

Circuit Connection (Reverse Bias)

  • Reverse the terminals:
    • Negative terminal connected to diode's p-type.
    • Positive terminal connected to ground.
  • Replace the ammeter with a microammeter (due to smaller currents).

Forward Bias Characteristics

  • Initial Observations:

    • At 0.1V, 0.2V, 0.3V, and 0.4V, minimal change in current.
    • Slight current increase starts at 0.5V.
    • At 0.6V, current increases to approximately 3.6 mA.
    • At 0.7V (cut-in voltage), current increases drastically (maximum ~25.2 mA).

  • Key Point:

    • Cut-in Voltage for Silicon Diode: 0.7V.
    • Cut-in voltage: The voltage at which the diode begins to conduct significantly.

Reverse Bias Characteristics

  • Initial Observations:
    • Use microammeter for smaller currents.
    • At 0.1V, current is 0.1 μA.
    • At 0.2V, current is 0.2 μA, and so on in a linear fashion.
    • Linear relationship continues up to 6V, where current equals voltage.

Characteristics Graph

  • Forward Bias:
    • Graph shows a gradual increase in current up to 0.7V, followed by a steep rise.
  • Reverse Bias:
    • Linear characteristics drawn in the third quadrant (negative values).

Summary

  • The experiment demonstrates the distinct characteristics of a p-n junction diode under forward and reverse biases.
  • Forward bias reveals a threshold (cut-in) voltage where the diode conducts significantly.
  • Reverse bias shows linear characteristics due to small currents and requires a microammeter for measurement.

Full transcript