Practical No. 08: Determination of static and dynamic resistance of given P N junction diode.

 Practical No. 08: Determination of static and dynamic resistance of given P N junction diode.

• The forward resistance (both static and dynamic) was low, while the reverse resistance was very high. The knee voltage was identified, and the values of static and dynamic resistance were calculated from the graph.

• It is concluded that a PN junction diode conducts easily in forward bias and offers very high resistance in reverse bias.
• It is recommended to carefully limit the current in forward bias and the voltage in reverse bias to avoid damaging the diode.

• Answer: For a Silicon diode (e.g., IN4007), the knee voltage is approximately 0.7 V. For a Germanium diode, it is approximately 0.3 V.

• Answer:
  1. Set the multimeter to diode test mode.
  2. Connect the red probe to one terminal and the black probe to the other.
  3. If the meter shows a reading (between 0.5V to 0.8V for Si), the terminal connected to the red probe is the P-side (Anode) and the black is the N-side (Cathode).
  4. If the meter shows “OL” or “1”, the connections are reversed.

• Answer: The current in reverse bias is very small (in microamperes or even less). Using an ammeter with a higher range (e.g., milliammeter) would not give a measurable or accurate reading for such a small current.

• Answer: The diode used was IN4007. Its specifications are:
  • Maximum Average Forward Current: 1 A
  • Peak Repetitive Reverse Voltage: 1000 V
  • Forward Voltage Drop: ~1.1 V at 1 A

• Answer:
  • If forward biased: The diode is ON. Assuming a knee voltage (V_k = 0.7V for Si) drops across it, the current is:
    • Formula: I = (V_supply – V_k) / R
    • Given circuit simple calculation (as per manual text short note): I = V / R = 5 / 1000 = 0.005 A

  • If reverse biased: The diode is OFF. The current is approximately zero (only a very small leakage current flows).