The output impedance is a function of the channel resistance.Ī set of static characteristic curves (graphs) can be drawn to show the static characteristics of a field effect transistor for different DC operating voltages and currents. Thus the input resistance of the MOSFET through the gate terminal is extremely high with very low input leakage current. An insulating oxide layer forms the gate terminal insulating the channel from the gate. Two separate low-resistivity regions being the source and drain, are diffused into the substrate making an electrical connection through the channel. The MOSFET consists of a high resistivity semiconductor substrate material forming the conductive channel.

The current flow between the source and drain terminals is related to the drain-source voltage and the resistance of the channel. The other terminal is called the Drain terminal as current “drains” away from it.

One end of the silicon bar is called the Source terminal as electric current is “sourced” into it, since, as far as the JFET is concerned, current originates from this source terminal.

The operating principle of the JFET and MOSFET are very similar in that they are voltage controlled devices in that they can control a much larger source-drain current flowing through their conductive channel using an electric field.īasically the junction field effect transistor is nothing more than a piece of doped silicon which behaves as a variable resistor. FET’s use a conductive central channel to control the flow of current through themselves by the application of different voltages onto their connecting terminals.įET’s come in two basic types, the Junction FET (JFET) and the Insulated-gate FET known more commonly as a Metal-Oxide Semiconductor Field Effect Transistor, or MOSFET in either N-channel or P-channel configurations.įield Effect Transistors have three distinct terminals known as Source, Gate and Drain. The Field Effect Transistor, or FET, is a solid-state unipolar semiconductor device.

Field effect transistor download free