Please Answer ASAP. Thanks!
Posted: Tue May 24, 2022 8:54 am
Please Answer ASAP. Thanks!
Consider the BJT common-emitter amplifier in Figure 1. Assume that the BC548B transistor has the following parameters: B=335, Ve=0.7 V and the Early voltage V₁ = 500 V. We consider the room temperature operation (i.e., V+= 25 mV). 5.0V Vc Vin Vload 0.005Vpk 1 kHz Rg www 680 0 RB1 01 M RC BC5488 Cout 22 μF HH 10 μF Vb* RB2 RE Fig. 1 BJT common-emitter amplifier. Part 1 (a) Design the DC biasing circuit (i.e., find the values of resistors R1, R2, Rc and Rg) so that /c=2 mA, Vc = 1.8 V and V₁ = 1.2 V. [20 marks] (b) Use the DC operating point analysis in Multisim to calculate Ic, Vc, VB, VE and VCE. Compare your results with your hand calculations from (a) and explain any differences. [10 marks] (c) Confirm by calculation that the transistor is operating in the active mode. [5 marks] (d) Calculate the transistor small signal parameters gm, reand ro. [5 marks] (e) Assuming that the frequency is high enough that the capacitors appear as short circuits, calculate the mid-band small signal voltage gain A, = Vload/Vin- [10 marks] (f) Use the AC sweep analysis in Multisim to simulate the amplifier small signal voltage gain A₁ = Vload/Vin over the frequency range of 10 Hz to 100 MHz, using a decade sweep with 10 points per decade. Set the AC voltage source to a peak voltage of 0.005 V. Compare the simulated gain with the gain calculated in (e) above. Also, explain the shape of the simulated gain curve (why does the gain decrease at low frequencies and at high frequencies?). [15 marks] CE 4.7 uF Rload 5 ΚΩ
Part 2 In practical electronic circuits, the B of BJT can change from component to component. Assume that we use another piece of BC548B transistor, which has B=350+ the last two digits of your student number (e.g., if the last two digits of your student number is 50, then ß= 350+50-400). The VBE = 0.7V and the Early voltage V₁ = 500V are not changed. The same DC biasing circuit that you designed in Part 1 is used. With this new piece of BC548B transistor: (g) Calculate the DC biasing parameters IC, VCE and V₁. [5 marks] (h) Calculate the mid-band small signal voltage gain A, = Vload/Vin (assume that the frequencyis high enough that the capacitors appear as short circuits). [10 marks] (i) Use the AC sweep analysis in Multisim to simulate the amplifier small signal voltage gain A₁ = Vload/Vin over the frequency range of 10 Hz to 100 MHz, using a decade sweep with 10 points per decade. Set the AC voltage source to a peak voltage of 0.005 V. Compare the simulated gain with the gain calculated in (h) above. [10 marks] (i) Compare the gains obtained in Part 1 and Part 2. Based on the comparison, discuss the impact of BJT parameter variation (i.e., the change of B) on the performance of the amplifier circuit. [10 marks]
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Part 2 In practical electronic circuits, the B of BJT can change from component to component. Assume that we use another piece of BC548B transistor, which has B=350+ the last two digits of your student number (e.g., if the last two digits of your student number is 50, then ß= 350+50-400). The VBE = 0.7V and the Early voltage V₁ = 500V are not changed. The same DC biasing circuit that you designed in Part 1 is used. With this new piece of BC548B transistor: (g) Calculate the DC biasing parameters IC, VCE and V₁. [5 marks] (h) Calculate the mid-band small signal voltage gain A, = Vload/Vin (assume that the frequencyis high enough that the capacitors appear as short circuits). [10 marks] (i) Use the AC sweep analysis in Multisim to simulate the amplifier small signal voltage gain A₁ = Vload/Vin over the frequency range of 10 Hz to 100 MHz, using a decade sweep with 10 points per decade. Set the AC voltage source to a peak voltage of 0.005 V. Compare the simulated gain with the gain calculated in (h) above. [10 marks] (i) Compare the gains obtained in Part 1 and Part 2. Based on the comparison, discuss the impact of BJT parameter variation (i.e., the change of B) on the performance of the amplifier circuit. [10 marks]