Diode characteristics

# Materials Required

• A p-n junction diode
• 3 V battery
• 50 V battery
• High resistance rheostat
• 0-3 V voltmeter
• 0-50 V voltmeter
• 0-100 mA ammeter
• 0-100 µA ammeter
• One way key
• Connecting wires

# Real Lab Procedure

Forward V-I Characteristics : • Connections are made as per the connection diagram.
• Insert the key. Arrange the sliding contact of the rheostat to minimum.
• Now, gently move the rheostat contact to provide a positive bias voltage.
• Note the voltmeter and milli ammeter readings.
• Repeat the process by increasing the forward current in equal steps by changing the rheostat slider.
• It can be noted that, initially the current increase very slowly. For a certain value of voltage, it shows a sharp increase. The corresponding voltage represents the knee voltage of that diode.
• Plot a graph with forward voltage along X axis and forward current along Y axis. The graph shows the forward V-I characteristics of the given p-n junction diode.

Reverse V-I Characteristics : • Make the circuit diagram as shown in the figure.
• Insert the key. Arrange the sliding contact of the rheostat to maximum.
• Move the sliding contact of the rheostat to provide a reverse bias voltage.Note the voltmeter and micro         ammeter readings.
• Note the voltmeter and micro ammeter readings.
• Repeat the process by changing the reverse voltage in equal steps.
• The current increases slowly in the beginning and then rapidly when the reverse voltage becomes a certain value. This voltage is known as the reverse breakdown voltage.
• Plot a graph with reverse voltage along X axis and reverse current along Y axis. The graph shows the reverse V-I characteristics of the given p-n junction diode.

# Simulator Procedure (as performed through the Online Labs)

• Select the characteristics of diode from the drop down list.
• Select the diode from the drop down list.
• To see the circuit diagram, click on the 'Show circuit diagram' check box seen inside the simulator window.
• Connections can be made as seen in the circuit diagram by clicking and dragging the mouse from one connecting terminal to the other connecting terminal of the devices to be connected.
• Drag the key to insert it.
• You can change the rheostat resistance using the slider.
• You can select the room temperature using the slider.
• You can notice the corresponding ammeter and voltmeter readings.
• To redo the experiment, click on the ‘Reset’ button.

# Observations

Forward V-I Characteristics :

 Sl. No. Forward bias voltage, Vf (V) Forward current, If (mA) 1 2 3 4 5 6 7 8 9 10

Reverse V-I Characteristics :

 Sl. No. Reverse bias voltage, Vr  (V) Reverse current, Ir   (µA) 1 2 3 4 5 6 7 8 9 10

# Calculations

For the forward characteristics of the given p-n junction diode, a graph is plotted with forward voltage along X axis and forward current along Y axis. The forward current shows a sudden increase at certain forward voltage, which is known as the knee voltage.

For the reverse characteristics of the given p-n junction diode, a graph is plotted with reverse voltage along X axis and reverse current along Y axis. I t is noted that at a certain reverse voltage, the reverse current reaches its maximum level. Further increase in voltage does not increase this current. It is the reverse saturation current. However, with further increase in reverse voltage, the current shows a rapid rise at a certain value. It is known as the reverse breakdown voltage # Result

The forward and reverse characteristics of the given p-n junction diode is drawn.

Cite this Simulator: