cb lab2b
Figure 1. CB + EF Amplifier

1. Lab goals

Topics
  • Transistor small-signal model parameters and small-signal circuit analysis.

  • Prediction and measurement of amplifier input resistance, voltage gain, and output resistance.

2. DC solution

  • Calculate the DC values of all node voltages and collector currents in the CB + EF Amplifier circuit.

  • Build the circuit and measure the node voltages ("Ohm’s law" the collector currents) to verify that you have both done the calculations correctly and have a functioning amplifier.

3. AC circuit performance

3.1. Measurements

Set the signal generator to an ampliitude of 20 mVp-p at 1 kHz. The 50 Ω resistor is inside the generator and is its Thevenin-equivalent output resistance.

  • Measure the voltage gain of the amplifier vout / vin.

Use the concepts of equivalent input and output resistance to make a strategy to measure the amplifier’s Rin and Rout as shown in CB + EF Amplifier.

  • Measure the amplifier’s Rin and Rout using your technique.

3.2. Predictions

Re-draw the schematic as a cascade of two general voltage-in / voltage-out amplifiers. (see the whiteboard figure) Use this structure and your DC bias solutions to calculate each sub-amplifier’s input resistance, output resistance, and voltage gain.

From those numbers, predict the composite amplifier’s Rin, Rout, and voltage gain. This should include the effects of the signal generator’s output resistance and the load resistance.

4. References