Basic Electronics Paper 3, WASSCE (PC 2ND), 2021

Question 1

 

AIM: To determine the forward current voltage characteristics of Zener diode.
           

  1.   Connect the circuit diagram as shown in Figure 1.
  2.   Ask the Supervisor to check the circuit connection.
  3.   You are provided with Table 1.

Table 1


VS (V)

VD (V)

ID (mA)

0.0

 

 

0.5

 

 

0.8

 

 

1.0

 

 

2.0

 

 

5.0

 

 

8.0

 

 

10.0

 

 

  1.  Switch on the power supply unit.
  2. Set the input d.c. of the power supply unit to 0 V.
  3. Read and record the ammeter and voltmeter readings in Table 1
  4. Set the input d.c. of the power supply unit to 0.5 V.
  5. Read and record the ammeter and voltmeter readings.
  6. Repeat steps (g) and (h) for the other corresponding values of VS in Table 1.
  7. Switch off the power supply unit.
  8. Plot a graph of current I (mA) on the vertical axis against voltage VD (V) on the horizontal axis.
  9. From the graph, determine the knee voltage of the diode.

Observation

 

                                 

The expected responses were:
TABLE 1


         VS (V)

VD (V)

ID (mA)

0.0

0.0

0.0

0.5

0.2 - 0.5

0.2 – 0.3

0.8

0.3 – 0.7

0.5 – 1.0

1.0

0.3 – 0.7

1.0 – 1.5

2.0

0.3 – 1.1

2.5 – 7.5

5.0

0.4 – 1.1

8.5 – 10.5

8.0

0.4 – 1.1

14.0 – 18.0

10.0

0.4 – 1.1

18.0 – 22.0

(k)        A non-linear curve from origin (0, 0) in the positive space.
(l)         knee voltage of 0.3 – 0.7 V.