Lab8 Report Instructions

• Preparation:
  • 1- Use AC sweep in PSpice (Start Freq=1, End Freq=1G, Points=100) after changing V_sin to 1 Vac in fig. 8-1, show circuit schematic and trace ratio V_out/V_in (V_out is across R_L and V_in is V_sin) in dBs or 10log10(V_out/V_in), label the two 3-dB lower and higher frequency points where the ratio is equal to max(V_out/V_in) -3 dBs, what are the two frequencies found?
  • 2- Repeat all the above after changing all 3 capcitor values to 10u.
  • 3- Explain the difference in results caused by decreasing capacitors values.

• Procedure:
  • 1- Plot the VI characteristic for the BJT with 1K resistor obtained using "BJT_iv_curve.vi".
  • 2- Draw the load line for the circuit using eq. 8-1.
  • 3- Mark the Q point where one of the curves (corresponding to the I_B value closest to I_E in eq. 8-4) intersects the load line, show the corresponding I_C value found on the load line.
  • 4- Compute g_m using eq. 8-12, get Di_c and Dv_be using ""BJT_trans.vi"" of the two chosen points with i_c values around the I_C value found above for the Q point.
  • 5- Compute the gain from eq. 8-6.
  • 6- Show the Vp values for V_in and V_out and compute gain from experiment in lab for both used capacitor values, compute g_m from experimental gain, should there be a difference in gain values when changing the capacitor values?
  • 7- Plot the output to input ratio in dB for both capacitors obtained using "freqlog.vi", mark the two estimated Q points (for low and high freq), explain the differences (values and frequencies) occurring when changing capacitors.

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