As anyone involved in RF design will attest, this is a very useful attribute.Īlso the low input impedance can often able this to provide a good match to 50Ω, a useful attribute for many RF design scenarios. This occurs because the base, which is the electrode physically between the emitter and collector is grounded, thereby providing a barrier between the two.Īs a result, the common base configuration tends to be used for RF amplifiers where the increased isolation between input and output gives a greater level of stability and reduces the likelihood of unwanted oscillation. This transistor configuration is probably the least used, but it does provide advantages that the base which is common to input and output is grounded and this has advantages in reducing unwanted feedback between output and input for various RF circuit design applications. The other salient feature of this configuration is that the input and output are in phase. Although the voltage is high, the current gain is low and the overall power gain is also low when compared to the other transistor configurations available. This transistor configuration provides a low input impedance while offering a high output impedance. Common base transistor configurationĪlphabetically, this is the first transistor configuration, but it is probably the least likely to be used. These configurations have the same types of properties, although slightly modified for the type of electronic device used.įor FETs terms like common drain, common source and common gate are used, and for valves / tubes, terminology includes common cathode, common anode and common grid. There are equivalent circuit configurations for FETs, and also thermionic valves / vacuum tubes. grounded base, grounded collector and grounded emitter may also be used on occasions because the common element signal is normally grounded. This gives rise to the three terms: common base, common collector and common emitter. The naming of the three basic transistor configurations indicates the transistor terminal that is common to both input and output circuits. In addition to selecting the right circuit configuration or topology in the electronic circuit design stage, to provide the required basic performance, additional electronic components are placed around the transistor: typically resistors and capacitors, and the values are calculated to give the exact performance needed.īoth the selection of the topology and the calculation of the electronic component values are key elements of the electronic circuit design process. The three different transistor circuit configurations are: common emitter, common base and common collector (emitter follower), these three circuit configurations have different characteristics and one type will be chosen for a circuit dependent upon what is required.Įach has different properties in terms of the gain, and input and output impedance, etc and as a result, a particular configuration will be selected during the electronic circuit design process.Įach of the different transistor topologies has the inputs and outputs applied to different points, with one terminal common to both input and output. When considering the electronic circuit design for a transistor circuit there are three different basic circuit configurations that can be used. Transistor circuit design Circuit configurations Common emitter Common emitter circuit design Emitter follower Common base Transistor Circuit Design Tutorial Includes: Transistor Configurations: circuit configurations Transistor circuits use one of three transistor configurations: common base, common collector (emitter follower) and common emitter - one is selected during the electronic circuit design process.
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