Basic Electronics Paper 3, WASSCE (PC 2ND), 2020

Question 1

 

AIM: To investigate the characteristics of a diode transistor logic circuit.


 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

  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.
  4.  

     

  5.  Close switch (s)
  6. Set switches S1, S2 and S3 to low positions as indicated in Table 1.
  7. Observe and record in Table 1, the state of the LED as either ON or OFF.
  8. Repeat steps (e) and (f) for the other states of switches S1, S2 and S3 in Table 1.
  9. Open switch (s)
  10. From your result, state the logic gate implemented by the circuit in Figure 1.
  11. Draw the logic symbol of the gate in (i).
  12. Write the Boolean expression of the gate in (i).

Observation

 

The expected responses were:

(i)         AND gate (deduced from Table 1)