Experiment 5 - Voltages in a Common Emitter Circuit

How strongly does a common emitter circuit amplify voltage? For this measure the voltages at the input and output of the common emitter circuit.

Use the circuit shown.

Measuring voltage in a common emitter circuit. (Enlarge)

Circuit diagram voltage measurement in a common emitter circuit.

Turn the potentiometer P1, until a voltage of approx. V_in = 0.68 V applies to the base. At the same time you measure at the output a typical value of approx. V_out = 2.50 V.

Turn P1 a little further until a voltage of approx. V_in = 0.69 V applies to the base. Now you measure a typical value of approx. V_out = 1,75 V at the output.

A change of only 0.01 V at base results in a fall of 0.75 V at the output (inverting!).

The values can vary greatly in your experiments. Important however is the finding...

                           

The voltage gain of a common emitter circuit is high.

Since both current and voltage is amplified, another finding can also be stated...

                           

The power gain of a common emitter circuit is high.

Now you compare these results to a common collector circuit...?