The Common-Emitter Circuit

Schematic of the Common-Emitter Circuit with NPN- and PNP-BJT

The picture on the left shows the schematic of the common-emitter circuit with an NPN transistor. The picture on the right shows the schematic of the common-emitter circuit with a PNP transistor.

Common-Emitter Circuit with NPN-BJT Common-Emitter Circuit with PNP-BJT

Fields of Application for the Common-Emitter Circuit

The common-emitter circuit is a basic transistor amplifier with voltage gain and current gain. It has a medium input impedance and a medium output impedance. This circuit offers the highest power gain of the three basic transistor amplifier circuits. The common-emitter circuit is suited for an AC-voltage amplifier in a wide area of application. It is often used as an amplifier stage in audio circuits or radio frequency circuits.

Howto Design a Transistor Amplifier in Common-Emitter Configuration

Transistor amplifiers in common-emitter configuration can be designed with TransistorAmp 1.1 software. Open TransistorAmp software and click on New Amplifier - Common-Emitter circuit:

design a new amp in common-emitter configuration

Now, the dialog Common-emitter circuit appears. Here you must input all parameters of your amplifier circuit:

specify a new amp in common-emitter configuration

To select the transistor type for your circuit, you must click the button Select transistor type from list and choose the transistor type within the next dialog:

select a transistor type for the amplifier in common-emitter configuration

TransistorAmp software contains almost every usual type of bipolar transistor (thousands of types). So, you will surely find there the transistor type you need. After having chosen a transistor type, you must click on OK and you will get back to the previous dialog. Now, it contains the transistor type which you have selected. You can click on OK. Then, the dialog closes and you will see immediately the design result of your new transistor amplifier (click the picture for full size):

design result of your new transistor amplifier in common-emitter configuration

Here, you can see your input parameters, the circuit and the values of all components. Furthermore, you can see the most important parameters of the operation point, i.e. collector current, collector emitter voltage and power consumption.

If you want to change any parameter of the circuit, simply click again on New Amplifier - Common-Emitter circuit and you will see, that the input dialog remembers all of your inputs, so it is easy for you to make changes.

If you want to save your result, click on Result - Save:

save the design result of your new transistor amplifier in common-emitter configuration

Then, input a file name and save the file.

Here, you can see the result file from our example: Amplifier in common-emitter configuration