Basic Electronics Paper 3, WASSCE (SC), 2022

Question 2

 

 

 

AIM: The aim of the experiment is to investigate the operational function of a resistor- transistor logic circuit.

  1. Connect the circuit as shown in Figure 2.
  2. Ask the supervisor to check the circuit connection.
  3. You are given Table 2.

   
                                      Table 2


Sw1

Sw2

Vout (V)

Logic State

OFF

OFF

 

 

OFF

ON

 

 

ON

OFF

 

 

ON

ON

 

 

  1. Switch ON the power supply unit.
  2. Set switches sw1 and Sw2 to OFF positions.
  3. Read and records Table 2, the output voltage (Vout).
  4. Repeats step (e) and (f) for the other positions of switches Sw1 and Sw2 as shown in Table 2.
  5. Complete Table 2 by writing logic state ‘0’ for Vout  less than 1.5 V and logic state ‘1’ for Vout greater than 1.5 V.
  6. Switch OFF the power supply unit.
  7. Write the Boolean expression for the logic circuit.
  8. Draw the logic gate symbol for the circuit.

 

Observation

The expected responses were

:

Sw1

Sw2

Vout (V)

Logic State

OFF

OFF

8.0 - 9.9

1

OFF

ON

8.0 - 9.9

1

ON

OFF

8.0 - 9.9

1

ON

ON

0.1 - 0.9

0

 

 

 

(j)                                                                             

(k)      

            Both questions required candidates to connect circuit, measure and record readings of output voltage Vout (V) as input voltage Vin (V) is varied, thereafter, use the values obtained to plot a linear and a non-linear curve the same graph sheet. The Chief Examiner reported that though majority of the candidates obtained reasonable readings, very many of them were unable plot graphs as expected