Q. Explain about Junction FET?

The JFET is a three-terminal, voltage-controlled current device, whereas the BJT is principally a three-terminal, current-controlled current device. The advantages associated with JFETs are much higher input resistance (on the order of 10⁷ to 10¹⁰ ), lower noise, easier fabrication, and in some cases even the ability to handle higher currents and powers. The disadvantages, on the other hand, are slower speeds in switching circuits and smaller bandwidth for a given gain in an amplifier.

Figure shows the n-channel JFET and the p-channel JFET along with their circuit symbols. The JFET, which is a three-terminal device, consists of a single junction embedded in a semiconductor sample.When the base semiconductor forming the channel is of a n-type material, the device is known as an n-channel JFET; otherwise it is a p-channel JFET when the channel is

formed of a p-type semiconductor. The functions of source, drain, and gate are analogous to the emitter, collector, and base of the BJT. The gate provides the means to control the flow of charges between source and drain.