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Difference between JFET and MOSFET
There is a category of transistors called Field Effect Transistor (FET). In this category, a lot of field effect transistors are there like Junction Field Effect Transistor (JFET), Metal Oxide Field Effect Transistor (MOSFET), Metal Semiconductor Field Effect Transistor (MSFET), etc. In this article, we will compare and contrast the various features of JFET and MOSFET.
What is JFET?
JFET stands for junction field effect transistor. The JFET is a three terminal semiconductor device and the terminals are: Source (S), Drain (D) and Gate (G). JFET has a channel between source and drain. The channel is the path between the source and drain for current to flow.
Based on the nature of the channel the JFETs are of two types as −
- N-channel JFET
- P-channel JFET
The junction field effect transistor (JFET) can only be operated in the depletion mode. It is used in various application like voltage variable resistor, digital switch, amplifier, etc.
What is MOSFET?
MOSFET stands for metal oxide semiconductor field effect transistor. The MOSFET is a four terminal semiconductor device where the terminals are: source (S), drain (D), gate (G) and body (or substrate). MOSFET is a field effect transistor with a MOS structure. MOSFETs are high speed and low-loss operation transistors.
Depending upon the channel polarity, MOSFETs are also of two types as −
- N-type MOSFET
- P-type MOSFET
A MOSFET can be operated in both enhancement mode with normally OFF and depletion mode with normally ON by control method. Enhancement type MOSFET is most popular.
MOSFETs are widely used in IC design, amplifier for high noise applications, speed controllers, etc.
Difference between JFET and MOSFET
The following table highlights the key differences between junction field effect transistor (JFET) and metal oxide semiconductor field effect transistor (MOSFET).
| Parameter | JFET | MOSFET |
|---|---|---|
| Full form | JFET stands for Junction Field Effect Transistor. | MOSFET stands for Metal Oxide Semiconductor Field Effect Transistor. |
| Terminals | JFET is a three terminal device, where the terminals are named – Source (S), Drain (D) and Gate (G). | MOSFET is also a four terminal device, where the terminals are – Source (S), Drain (D), Gate (G) and Body or Substrate (B). |
| Mode of operation | JFET operates only in depletion mode. | MOSFET can be operated in both enhancement mode and depletion mode. |
| Gate terminal | JFET has a gate terminal which is not insulated from the channel. | The gate terminal of the MOSFET is insulated from thin layer of metal-oxide. |
| Channel | JFET has a continuous channel. The channel exists permanently. | MOSFET has a continuous channel only in depilation type, but not in the enhancement type. Thus, the channel exists permanently in depletion type, but not in enhancement type. |
| Types | JFETs are of two type: N-channel JFET and P-channel JFET. | MOSFETs are of four types: P-channel enhancement MOSFET, P-channel depletion MOSFET, N-channel enhancement MOSFET and N-channel depletion MOSFET. |
| Input impedance | JFET has a high input impedance which is of the order of 109 $\Omega$. | MOSFET has very high input impedance of the order of 1014 $\Omega$. |
| Susceptible to damage | JFET is less susceptible to damage as it has high input capacitance. | MOSFET is more susceptible to damage because the presence of metal oxide reduces input capacitance. |
| Manufacturing process | The manufacturing process of JFET is simple and less sophisticated. | Manufacturing of MOSFET is complex. |
| Drain resistance | The drain resistance of JFET is high and ranges from 105 Ω to 106 Ω. | The drain resistance of MOSFET is low of the order of 1 Ω to 50 Ω. |
| Manufacturing cost | The manufacturing cost of a JFET is less than MOSFET. | The addition of metal oxide increases the manufacturing cost of MOSFET. Thus, MOSFET is expensive than JFET. |
| Gate current | For JFET, gate current is more. | For JFET, gate current is more. |
| Characteristics curve | JFET has more flat characteristics curve. | MOSFET has relatively less flat characteristics curve. |
| Conductivity control | In JFET, the conductivity of the device is controlled by the reverse biasing of the gate. | In MOSFET, the conductivity is controlled by the charge carriers induced in the channel. |
| Signal handling capacity | The signal capacity of the JFET is less. | MOSFET has more signal handling capacity than JFET. |
| Applications | JFET is mainly used in low noise applications. | MOSFET is extensively used in high noise applications. |
Conclusion
From the above discussion, it can be concluded that there are various differences between junction field effect transistor (JFET) and metal oxide semiconductor field effect transistor (MOSFET). Both of these transistors are widely used in different electronic circuit applications. Hence, the knowledge of these differences can help an individual to select either of them according to the exact requirements.
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