Experiment

1.

Determine the value of g_m and theoretically recalculate the voltage gain using Equation (2.24). Compare your results with the theoretical results. Does inclusion of $\Delta V_{be}$ give results which are in better agreement with experiment?

2.

Build the circuit in Fig. 2.8.

  

Figure 2.8: CE Amp with R_E=0

Notice that the 200K resistor provides the base current necessary for establishing a DC bias.

3.

Measure the DC voltages to make sure the BJT is in the forward active region. If it's not in forward active, adjust your resistor values to compensate.

4.

Perform a small signal theoretical analysis to predict what the voltage gain of the circuit should be.

5.

Measure the voltage gain. Adjust the input signal from your wavetek to approximately 10mV amplitude, with a frequency of 100kHz. What is the voltage swing? (If your signal source cannot reach as low as 10mV, you can use a simple voltage divider to achieve the required level.)

6.

Do the measured values for gain and swing agree with your theoretically predicted ones to within 25% error?

7.

Design: Theoretically determine what new value of R_C you need to reduce the gain by 50% of what your measure above. What is the new swing.

8.

Substitute this new value of R_C and measure the gain and the swing. Does the values agree with your theoretically predicted values to within 25% error?