cb lab2b
Figure 1. CB + EF Amplifier

1. Lab goals

  • 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 Figure 1, “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 amplitude 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 Figure 1, “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.

See the Guidebook bjt-amplifiers.html.

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.