PLEASE USE MULTISIM
Posted: Thu May 26, 2022 10:54 am
PLEASE USE MULTISIM
Consider the BJT common-emitter amplifier in Figure 1. Assume that the BC548B transistor has the following parameters: B= 335, VBE = 0.7 V and the Early voltage VA = 500 V. We consider the room temperature operation (i.e., VT = 25 mV). 5.0V Vcc Vin Vload V1 0.005Vpk .1 kHz 0° Cin www HH RB1 Rg www 680 Q 10 μF Vb RB2 RE Fig. 1 BJT common-emitter amplifier. www Q1 RC A Vc Cout HH 22 μF BC548B CE 4.7 μF Rload 5 ΚΩ
Part 1 (a) Design the DC biasing circuit (i.e., find the values of resistors RB₁, RB2, RC and RE) so that /c = 2 mA, VCE = 1.8 V and VE = 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, rand 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 A₂ = 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]
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Part 1 (a) Design the DC biasing circuit (i.e., find the values of resistors RB₁, RB2, RC and RE) so that /c = 2 mA, VCE = 1.8 V and VE = 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, rand 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 A₂ = 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]