Experiment: Study of Diode Characteristics

Theory: -
A p-n junction is a two-terminal device that acts as a one-way conductor. When a diode is forward biased as shown in Figure1 (a), Current flows through the diode and current is given by

I_D = I_S (e ^Vo/nV_T – 1) ------ (1)

When, n is the ideality factor and 1 ≥ n ≥ 2. I_S is the reverse-saturation current and V_T = KT/ q is the thermal voltage. V_T is about 0.026V at room temperature.

When it is reverse biased as shown in Figure, I_D = - I_S. As it is generally in P^A (Pico-Amp) range, in many applications this current is neglected and diode is considered open

I_D = I_S (e ^–V_R^/V_T - 1) = - I_S for | V | >> V_T ------- (2)

The material for p-n junction diode is silicon semiconductor. Semiconductors are a group of materials having electrical conductivity intermediate between metals and insulators. Metals: Al (Aluminum), Cu (Copper), Au (gold), Insulators: Ceramic, Wood, Rubber. Semiconductor: Si (Silicon), Ge (Germanium), GaAs (Gallium-Arsenide).

Apparatuses: -

· p-n junction diode (1N4003) ---- 1 Piece

· 5V Zener Diode ------------------- 1 Piece

· Resistor (1K) ---------------------- 1 Piece

· DC Power Supply ---------------- 1 Piece

· Signal Generator ----------------- 1 Piece

· Oscilloscope ---------------------- 1 Piece

· Chords and Wire ----------------- Lot

Data Table of Forward Region: -

VS (Volt)	VR Ω	VD (Volt)	ID (mA)
0.1	0	0.16	0
0.5	0.12	0.46	0.12
0.7	0.24	0.5	0.24
1.0	0.5	0.53	0.5
1.5	1.0	0.36	1.0
2.0	1.5	0.6	1.5
2.5	2.0	0.6	2.0
3.0	2.5	0.61	2.5
3.5	3.0	0.62	3.0
4.0	3.5	0.63	3.5
4.5	4.0	0.63	4.0
5.0	4.5	0.63	4.5

Data Table of Reverse Region: -

(Volt)	VR Ω	VD (Volt)	ID (mA)
0.1	0	0.15	0
0.3	0	0.34	0
0.5	0	0.54	0
0.7	0	0.72	0
1.0	0	1.03	0
2.0	0	2.05	0
3.0	0	3.11	0
4.0	0	4.06	0
5.0	0.04	5.05	0.04
6.0	0.52	5.56	0.52

Procedure: -

1. Measure resistance accurately using multimeter. Construct the circuit as shown in Figure- 2. Vary input voltage (V_dc) and measure V_D, V_R for values of V_D = 0.1V, 0.2V, 0.3V, 0.4V, 0.5V, 0.6V, 0.7V and so on. Obtain maximum value of V_D without increasing V_dc beyond 25V (Note that I_D = V_R/R).
2. Repeat step-1 for the values at V_Z = 0.5V, 1.0V, 1.5V, 2.0V, 2.5V, 3.0V and so on up to the maximum value obtainable without increasing V_dc beyond 25V. Apply circuit in Figure-3 for this step.
3. Construct the circuit as shown in the Figure-4. Set the oscilloscope in X-Y mode and locate the zero point on oscilloscope display. Make proper connection (according to Figure-4) and observe the output.
4. Repeat step-3 by increasing supply frequency to 5 KHz.

Report: -

1. Plot diode I-V chrematistics for different reading obtained in this experiment.
2. Explain the result obtained in Figure-1, 2, 3, 4.