ترانزستور الاثر المجالي .. الالكترونيات

Field Effect Transistor.. Electronics

Field Effect Transistor

It includes a source, a gate, and a drain. Its channel may be of type M or type S. Figure (277) shows one of the field effect transistors, which contains a gate of type M and a channel of type S. In it, electron carriers flow from the source to the drain. If the gate voltage changes, the current passing through the channel and the external circuit changes. The current is at its highest in the case of zero gate voltage (A), in which case the current passes easily. In the case of a small negative voltage across the gate, the carriers are exhausted from the channel and the current is smaller (B), i.e. its passage through the gate decreases. The more negative the voltage value increases, the channel narrows until it reaches the point of final depletion, or "final closure", so that it does not allow the current to pass through it (C). This transistor is characterized by a high input resistance, and thus imposes a small load on the circuit supplying its gate. It is known that the operation of ordinary transistors is done by the flow of current in the base and thus drawing a current that loads the base circuit itself.

As for the field effect transistor, it is controlled by the voltage applied to its gate. We see in Figure (278) an audio amplifier that uses a transistor of this type, which has become widely used in radios and other devices.

277 - Field effect transistor.
278 - Amplification circuit with a field effect transistor