Coursework EEE109
February 25, 2025
1 Question 1 (4 Marks)
Consider the Zener Diode circuit shown in Figure 1. Consider the following parameters: VI = 20V, VZ = 10V, Ri = 220Ω and PZ (max) = 440mW.(It is recommended that the calculation process be made to one decimal place.)
(a) If the load resistor is RL = 380Ω . Please calculate the load current IL , zener diode current IZ , and input current II (2 marks)
(b) Determine the value of RL that will establish PZ (max) (2 marks)
Figure 1: zener diode circuit
2 Question 2 (10 Marks)
The input voltage source is a square wave, as shown in Figure 2.
Figure 2: input voltage source
(a) Plot the waveform of output voltage Uo in circuit shown in Figure 3. Assume the turn-on voltage of the diode is Uγ = 0.6V. Please mark the maximum and minimum values on your figure. (5 marks)
(b) Plot the waveform of output voltage Uo in circuit shown in Figure 4. Assume the turn-on voltage of the diode is Uγ = 0.6V. Please mark the maximum and minimum values on your figure. (5 marks)
Figure 3: circuit I
Figure 4: circuit II
3 Question 3 (10 Marks)
The two diode circuit is shown in Figure 5. Calculate the output voltage vo and the diode current ID1 and ID2 for the following voltage conditions: Vγ = 0.6V and rf = 0Ω
Figure 5: two diodes circuit
(a) v1 = 10V and v2 = 0V (5 marks)
(b) v1 = v2 = 0V (5 marks)
4 Question 4 (10 Marks)
A full wave rectifier circuit with battery charging is shown in Figure 6. Assume VB = 9V,Vγ = 0.7V and vs = 15sin[2π (60)t](V).Assume rf=0Ω
Figure 6: full wave rectifier circuit with battery charging
(a) Determine the resistance of R such that the peak battery charging current is 1.2A (2 marks)
(b) Determine the average battery charging current (use the resistance value in (a)) (4 marks)
(c) Determine the fraction of time that each diode is conducting (4 marks)
5 Question 5 (6 Marks)
An NPN transistor with β = 80 is connected in a common-base configuration, as shown in Figure 7. The emitter is driven by a constant-current source with IE = 1.2mA. Determine the value of IB , IC , α and VC
Figure 7: npn with common base configuration
6 Question 6 (10 Marks)
Consider the circuit shown in Figure 8, VEB (on) = 0.7V. Use the Thevenin Equivalent Circuit to solve the following questions.
Figure 8: BJT circuit
(a) Please determine the value of RTH , VTH , IBQ , ICQ , and VECQ for β = 90 (5 marks)
(b) Determine the percent change in ICQ and VECQ if for β is changed to for β = 150 (5 marks)
7 Question 7 (14 Marks)
For the common-gate circuit in Figure Q7, theNMOS transistor parameters are: VTN = 1 V, kn = 3 mA/V2 , and λ = 0. Assume RS = 10 kΩ, RD = 5 kΩ and RL = 4 kΩ . Capacitors can be treated as short circuits in ac analysis.
Figure Q7
(1) Determine the Q-point of the transistor, values of IDQ and VDSQ. (6 marks)
(2) Draw the small-signal equivalent circuit. (4 marks)
(3) Find the small-signal voltage gain Av. (4 marks)
8 Question 8 (16 Marks)
Consider the circuit in Figure Q8, the transistor parameters are β = 100, VBE(on) = 0.7 V, VT = 0.026 V and VA = 100 V. The circuit parameters are R1 = 27kΩ, R2 = 15kΩ, Rc = 2.2kΩ, RE = 1.2kΩ, Rs = 10kΩ, RL = 2kΩ, and Vcc = 9V. Capacitors can be treated as short circuits in ac analysis.
Figure Q8
(1) Find the Q-point of the transistor in dc analysis. (5 marks)
(2) Draw the small signal equivalent circuit and determine the input resistance. (8 marks)
(3) Find the small signal voltage gain Av. (3 marks)
9 Question 9 (20 Marks)
You are required to design a MOSFET amplifier circuit for a telephone circuit with amidband frequency range of 300 Hz to 2 kHz. The desired magnitude of the midband voltage gain is 15.
Assume: VTN = 1V, IDQ = 0.2 mA, λ = 0 , VDSQ = 5 V, Rsi = 0, R1 + R2 = 200 kΩ .
Calculate the required values for the resistors R1, R2, RD and capacitors CC , CL , and the transistor parameter kn.
Figure Q9