3.9 Exercises

Assume diodes are silicon unless stated otherwise

Analysis Problems

1. Determine β if α = 0.99
2. Determine α if β = 200
3. Determine the currents for the circuit of Figure 3.9.1 if V_BB = 5 V, V_CC = 20 V,
   R_B = 200 kΩ, R_C = 2 kΩ, β = 100.
4. Determine the transistor voltages for the circuit of Figure 3.9.1 if V_BB = 5 V, V_CC = 20 V,
   R_B = 200 kΩ, R_C = 2 kΩ, β = 200.

   

5. Determine the LED current in the circuit of Figure 3.9.2 if V_logic = 5 V, V_CC  = 5 V,
   V_LED = 2.1 V, R_B = 3.6 kΩ, R_C = 270 Ω, β = 100.
6. Determine the LED current in the circuit of Figure 3.9.2 if V_logic = 0 V, V_CC = 5 V,
   V_LED = 2.1 V, R_B = 3.6 kΩ, R_C = 270 Ω, β = 100.
7. Determine the LED current in the circuit of Figure 3.9.3 if V_logic = 5 V, V_EE = 5 V,
   V_LED = 2.2 V, R_B = 2.7 kΩ, R_C = 220 Ω, β = 100.

   

8. Determine the LED current in the circuit of Figure 3.9.3 if V_logic = 0 V, V_EE = 5 V,
   V_LED = 2.2 V, R_B = 2.7 kΩ, R_C = 220 Ω, β = 100.
9. Determine the LED current in the circuit of Figure 3.9.4 if V_logic = 3.6 V, V_CC = 10 V,
   V_LED = 2.3 V, R_E = 270 Ω, β = 200.

   

10. Determine the LED current in the circuit of Figure 3.9.4. V_logic = 0 V, V_CC = 10 V,
    V_LED = 2.3 V, R_E = 270 Ω, β = 200.
11. Using the 2N3904 data sheet, determine V_CE(sat) if I_C = 30 mA and I_B = 1mA.
12. Using the 2N3904 data sheet, determine the percent change in β if I_C = 10 mA and the temperature rises from 25°C to 125°C.
13. Using the 2N3904 data sheet, determine the percent change in β if I_C = 40 mA and the temperature drops from 25°C to −55°C.

Design Problems

14. Using Figure 3.9.1, determine a value for R_B to set I_C to 5 mA if V_BB = 5 V, V_CC = 25 V,
    R_C = 2 kΩ, β = 100.
15. Using Figure 3.9.1, determine a value for R_C to set V_CE to 6 V if V_BB = 10 V, V_CC = 25 V,
    R_B = 330 kΩ, β = 200.
16. For the circuit of Figure 3.9.2, determine a value for R_C to set the LED current to 15 mA. V_logic = 5 V, V_CC =5 V, V_LED = 1.6 V, R_B = 3.3 kΩ.
17. For the circuit of Figure 3.9.3, determine a value for R_C to set the LED current to 20 mA. V_logic = 0 V, V_EE = 5 V, V_LED = 2.0 V, R_B = 2.7 kΩ.
18. For the circuit of Figure 3.9.4, determine a value for R_E to set the LED current to 25 mA. V_logic = 5 V, V_CC = 9 V, V_LED = 2.8V.

Challenge Problems

19. Determine the maximum and minimum values for I_C in the circuit of Figure 3.9.1 if all resistors have a 10% tolerance and β = ranges from 100 to 200.
    V_BB =5 V, V_CC = 20 V, R_B = 200 kΩ, R_C = 2 kΩ.
20. Derive and draw a PNP non-saturating LED driver circuit.

Computer Simulation Problems

21. Simulate the circuit of Problem 3.
22. Simulate the circuit of Problem 5.
23. Simulate the circuit of Problem 7.
24. Verify the design of Problem 14 using a simulator.