3-4. Junction Field-Effect Transistors (JFETs)

<Operation of JFETs>
JFET : Junction Field-Effect Transistor
(1) In the N-channel junction field-effect transistor (Fig. 3-3 (a)), when a voltage is applied between the drain and the source, electrons flow from the source to the drain.
(2) When a reverse bias is applied between the gate and source, the depletion layer expands and suppresses the electron flow in (1). (Narrowing path of electron flow)
(3) If the reverse bias voltage between the gate and source is further increased, the depletion layer blocks the channel and the flow of electrons stops.

As shown above, voltage applied between gate and source controls the condition between drain and source. So FETs are voltage-driven devices.

Symbol and operation of N-channel-type JFET
Fig. 3-3(a) Symbol and operation of N-channel-type JFET
Symbol and operation of P-channel-type JFET
Fig. 3-3(b) Symbol and operation of P-channel-type JFET

Note: Direction of current flow is opposite to that of  electron flow. The mechanism of widening of the depletion layer is the same as for diode.

Chapter III : Transistors

3-1. Types of Transistors
3-2. Bipolar Transistors (BJTs)
3-3. Bias Resistor Built-in Transistors (BRTs)
3-5. Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFETs)
3-6. Differences between BJT and MOSFET
3-7. Structure and Operation of MOSFET
3-8. MOSFET Performance Improvement: Decision Factors of RDS(ON)
3-9. MOSFET Performance Improvement: Approach to Low RDS(ON)
3-10. MOSFET Performance Improvement: Super-Junction MOSFETs (SJ-MOS)
3-11. Summary of MOSFET Features by Structure
3-12. Performance of MOSFETs: Drain Current and Power Dissipation
3-13. Performance of MOSFETs: Avalanche Capability
3-14. Performance of MOSFETs: Characteristic of Capacitance
3-15. Performance of MOSFETs: Safe Operating Area(or Area of Safe Operation)
3-16. Insulated-Gate Bipolar Transistors (IGBTs)
3-17. Operation of Insulated-Gate Bipolar Transistors (IGBTs)
3-18. Performance Improvement of IGBTs: Evolution of Vertical Design
3-19. What are RC-IGBTs and IEGTs?
3-20. Application of IGBTs
3-21. Comparison of Forward Characteristics of IGBTs and MOSFETs
3-22. Comparison of Transistors by Structure
3-23. Datasheets of MOSFET: Maximum Ratings
3-24. Datasheets of MOSFET: Electrical Characteristics
3-25. Datasheets of MOSFET: Capacitance and Switching Characteristics
3-26. Datasheets of MOSFET: Body Diode

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