The common-collector circuit

Schematic of the common-collector circuit with NPN- and PNP-BJT

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

Common-Collector Circuit with NPN-BJT Common-Collector Circuit with PNP-BJT

Fields of application for the common-collector circuit

The common-collector circuit is a basic transistor amplifier with current gain. It has a high input impedance and a low output impedance. The voltage gain is slightly lower than one.

The common-collector circuit is suited as a driver stage for connecting with a low impedance load. This application is called an impedance converter.

How to design a transistor amplifier in common-collector configuration

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

design a new amp in common-collector configuration

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

specify a new amp in common-collector 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-collector configuration

TransistorAmp software contains almost every usual type of bipolar transistor (thousands of types). So, you will certainly 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 (where you specify your amplifier). Now, that dialog contains the transistor type which you have selected and 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-collector 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-Collector 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-collector configuration

Then, input a file name and save the file.

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