Junction Field Effect Transistor

 The Junction Field Effect Transistor, or JFET, is a voltage controlled three-terminal unipolar semiconductor device available in N-channel and P-channel configurations In the Bipolar Junction In transistor tutorials, we saw that the output Collector the current of the transistor is proportional to input current flowing into The base terminal of the device, thereby making the bipolar transistor a “CURRENT” operated device (Beta model) as a smaller current can be used to switch a larger load current.

The Field Effect Transistor, or simply FET however, uses the voltage that is applied to their input terminal, called the Gate to control the current flowing through them resulting in the output current being proportional to the input voltage. As their operation relies on an electric field (hence the name field effect) generated by the input Gate voltage, this then makes the Field Effect Transistor a “VOLTAGE” operated device.

The junction Field Effect Transistor is a three-terminal unipolar semiconductor device that has very similar characteristics to those of their Bipolar Transistor counterparts. For example, high efficiency, instant operation, robust and cheap and can be used in most electronic circuit applications to replace their equivalent bipolar junction transistors (BJT) cousins.

Field effect transistors can be made much smaller than an equivalent BJT transistor and along with their low power consumption and power dissipation makes them ideal for use in integrated circuits such as the CMOS range of digital logic chips.