JFET and MOSFET are types of FET which is a group of field-effective transistors, devices the operation of which is connected with electrostatic modulation of conductivity between the source and drain.
JFET (junction gate field-effect transistor) and MOSFET (metal-oxide-semiconductor field-effect transistor) can be used as switches and amplifiers.
JFETs are the simplest field-effect semiconductor transistors with three terminals. Reverse biased PN junction isolates gate of the JEFT from the channel. Most popular applications of JFETs include amplifiers, electronically-controlled switches and voltage-controlled resistors.
MOSFETs' metal gate isolation from the channel is provided by semiconducor oxide. Four-terminal MOSFETs are basically used as switches and amplifiers, just like JFETs. Unlike JFETs, they can be fabricated in both depletion and enhancement forms.
In general, JFET and MOSFET are similar in their functions, applications and electrical characteristics.
Some of their key differences are listed below:
- MOSFET can be operated in both depletion and enhancement mode. JFET can only be operated in the depletion mode.
- MOSFETs have lower leakage current because their input impedance is higher than JFETs’, although the input impedance of JEFTs is still quite high.
- Characteristic curves of JFET are more flat than the curves of MOSFET. It is connected with different drain resistance which is high for JFETs and low for MOSFETs.
- They have different ways to control the current: for MOSFETS it is an isolated gate while JFETs use PN junction.
- Conductivity is controlled by the reverse biasing of the gate in JFET while in MOSFET – the carriers induced in the channel are used for this purpose.
- JFETs are rather static insensitive, while MOSFETs may lack the static protection diodes what makes them static sensitive due to the fact that they have a thin gate oxide layer.