1/13/2024 0 Comments Bjt structureWhen there is current from the collector to the emitter, it is said that the transistor is in saturation. The emitter current (Ie) is the sum of the currents of the base (Ib) and the collector (Ic). The result is that a small current in the base can control a bigger current which flux from the collector to the emitter like a key. Many electrons from the emitter will be attracted by the P material of the collector. When the VBE reach a voltage high enough to surpass the potential barrier of the junction between base (B) and the emitter (E), which usually is 0,7 V, generate a current in the base (the middle terminal). In this situation it is said that the transistor is in cutoff. When the VBE voltage is zero, there is no current flux, because a transistor’s junction will always be in the reverse mode. The transistor needs two voltage signals to work. Representation of BJTs in circuit schematics, NPN in the left and PNP in the right.Īs you can see, the middle layer linked to the base terminal is much thinner. These diodes won’t work as transistors, because there is metallic wire between the middle layers. To know more about diodes click in this button. While N is silicon doped with an element which has 5 electrons in the last layer (usually phosphorus). The bipolar junction transistor (BJT) has two types of layer structure: NPN in the right and PNP in the left.Īs I explained in the post about diodes, the P layer is silicon doped with an element which has 3 electrons in the last layer (usually boron). This is one of the most important electronic components. Exist many other types of transistors which will stay to other posts. In this post I will explain how the BJT (Bipolar Junction Transistor) works.
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