Basic Operation:
JFETs (Junction Field-Effect Transistors) are kind of like spigots. Using the image below, I’ll explain my analogy of an N-Channel JFET.
The Gate, formed by two p-type regions within the n-channel (which are connected internally), acts as the valve body (handle, stem, packing, etc.) This will restrict the flow of water- and current real-world. In a JFET the Gate is reverse-biased regardless of the channel type.
The Source and Drain act as the supply pipe and outlet. When the valve body is open (the VGG is 0 V) water (current supplied by VDD) can flow freely from the supply pipe to the outlet (Source to Drain.) When the valve body starts to close (VGG is increased), the water (current) begins to be restricted. Real-world, this is due to the p or n-type gate increasing it’s depletion layer respectively.
It is important to note:
- The current (ID) flows differently in P or N-Channel JFETs.
- P-Channel current flows by holes only.
- N-Channel current flows by electrons only.
- In N-Channel JFETs, The negative terminal of VGG is connected to the Gate and the negative terminal of VDD is connected to the Source.
- This is opposite in P-Channel JFETs.
- The depletion region is widest near the drain-end due to the reverse-bias voltage being greater between the gate and drain than that of the gate and source.
Uses:
JFETs can be used many different ways. They can be used as a constant current source, an electronic switch, a VRR, even various types of amplifiers.
Resources:
Floyd, T. L. (2017). Electronic Devices (Conventional Current Version) (10th ed.). Pearson Education (US).
School of Physics. (2020, December 14). Working of JFET | How JFET works? | JFET working animation. YouTube. Retrieved February 22, 2023, from https://www.youtube.com/watch?v=qtK3uA4gAoc
Semiconductor For You. (2021, May 29). What are the applications of JFET (junction field effect transistor)? Semiconductor for You. Retrieved February 22, 2023, from https://www.semiconductorforu.com/applications-jfet-junction-field-effect-transistor/
