Difference Between JFET and MOSFET

Difference Between JFET and MOSFET

JFETs, also known as field-effect transistors, are electrical devices that may be used as amplifiers or switches. They have become a vital feature of memory chips due to their high efficiency and low power consumption. JFET and MOSFET are two types of field-effect transistors (FETs) that operate on the same concept as junction transistors but are fundamentally different from one another.


While both JFET and MOSFET are semiconductor devices, their differences are as follows: the current through a JFET is channeled by an electric field across the reverse-biased PN junction, whereas in a MOSFET, the conductivity is due to a transverse electric field in the metal-oxide insulator embedded on the semiconductor.

The second significant distinction between the two is that the JFET has a lower input impedance than the MOSFET, and since the latter has an insulator integrated into it, it has a lower current leakage.

The JFET, which is commonly referred to as an “ON device”, is a depletion-type tool with low drain resistance, whereas the MOSFET, which is commonly referred to as an “OFF device”, can operate in both depletion and enhanced modes and has a high drain resistance, is a transition-type tool with low drain resistance.

What exactly is JFET?

Junction Gate Field Effect Transistor (JFET) is an acronym for Junction Gate Field Effect Transistor and is a unipolar device that is composed of three fundamental components: a source, drain, and gate. It is primarily used in the manufacture of amplifiers, resistors, and switches.

When a little voltage is given to the gate terminal of this kind of FET, it operates as a basic device. This modest voltage permits the current to travel from the source to the drain and even farther than that.

VGS is the voltage supplied to the gate of the semiconductor, and it is this voltage that regulates the width of the depletion zone and, therefore, how much current flows through the semiconductor. As a result, the drain current that flows through the channel is proportional to the voltage applied to the channel.

As the negative voltage applied to the gate terminal grows, the depletion zone expands and less current flows through the channel until it reaches a point where the depletion zone totally ceases the current flow. This is known as the saturation point.

JFETs are further divided into two types: N-Channel JFETs, in which the channel that links the drain and source is severely doped with electrons, and P-Channel JFETs, in which the channel is extensively doped with holes. N-Channel JFETs are used in high-speed switching applications.

What exactly is a MOSFET?

MOSFET, also known as Metal oxide semiconductor FET, is a high-performance version of the FET that consists of four pieces that work together to perform its duties. They are commonly utilized in computer memory chips, such as metal oxide semiconductor memory cells, for storing bits, and are very effective at doing so.

Despite the fact that MOSFETs operate on the same fundamental principles as FETs, their design is more complex, which increases their efficiency. Additionally, a MOSFET is a unipolar device that may be used to amplify signals in both the depletion and enhancement modes.

All varieties of MOSFETs feature a metal-oxide insulator between the substrate and the gate that keeps the two apart. When a voltage is supplied to the gate terminal, a channel is established between the drain and the source as a result of the electrostatic force, which permits the current to flow.

While the D-MOSFET operates in the depletion mode, in which a channel has already been formed, the E-MOSFET operates in the enhancement mode, in which a potential is required to build a channel before current can be carried through the device. This more sophisticated kind of transistor is designed to raise drain resistance and apply infinite input impedance while simultaneously decreasing leakage current. MOSFETs, on the other hand, need regular maintenance owing to the danger of corrosion that is connected with the metal oxide insulator.

Difference Between JFET and MOSFET

  • When comparing JFET and MOSFET, the primary difference is that current in JFET flows as a result of the electric field generated by the PN junction, while current in MOSFET flows as a result of the transverse electric field generated by the metal oxide layer.
  • Two other important differences are that JFETs have reduced input impedance and MOSFETs have almost infinite input impedance due to the lack of direct contact between the gate and the substrate
  • Third, although both JFET and MOSFET have low drain resistance, JFET has lower drain resistance while MOSFET has a large drain resistance.
  • JFETs have a larger leakage current as well, but MOSFETs have been engineered to be more efficient while exhibiting lower leakage current.
  • Despite the fact that JFETs are more complex to build than MOSFETs, they are less expensive than the latter.


Amplification and switching devices such as JFETs and their successor MOSFETs are extensively employed in a broad range of applications, including medical devices. MOSFETs, on the other hand, have evolved as more capable transistors that may be employed in computer memory chips.

The primary difference between the two is that a JFET employs an electric field at the PN junction to provide electrical conductivity through the substrate, while a MOSFET uses a transverse electric field in the embedded metal oxide layer to provide electrical conductivity through the substrate.

Another significant distinction is that the JFET does not have a metal oxide layer for insulation, but the MOSFET has, and it is for this reason that the MOSFET was given the moniker Metal Oxide Semiconductor Field Effect Transistor, or MOSFET.

The JFET is the most fundamental kind of FET, while the MOSFET was designed to be more efficient and to have less leakage current than the JFET. By inserting a metal oxide barrier between the gate terminal and the substrate, it was possible to obtain this result.

Despite the fact that JFET and MOSFET are members of the same transistor family, JFET is fundamentally different from its cousin MOSFET, which has far greater drain resistance and impedance than JFET does.

Because of the differences between JFET and MOSFET, each has a distinct area of use. For example, JFET is more often found in amplifiers, rectifiers, and switches, but MOSFET is more commonly found in computer memory chips due to its high degree of efficiency.