JFET vs. MOSFET Transistors

Field effect transistors (FETs) are used to amplify weak signals, mostly wireless signals. This is useful for aircraft, that often operate dozens if not hundreds of miles away from the signal’s source. A field effect transistor is a type of transistor that alters the electrical behavior of a device using an electric field effect to control the electrical conductivity of a channel. FETs are classified into JFET (Junction Field Effect Transistor) and MOSFET( Metal Oxide Semiconductor Field Effect Transistor). Both are mainly used in integrated circuits, and are similar in operating principles, but different in composition.

JFET is the simplest type of field effect transistor in which the current can pass either from source to drain or drain to source. Unlike bipolar junction transistors, JFET uses the voltage applied to the gate terminal to control the current flowing through the channel between the drain and source terminals which results in output current being proportional to the input voltage. Featuring a reverse-biased gate terminal, JFETs are three-terminal unipolar semiconductor devices used in electronic switches, resistors, and amplifiers. JFETs are more stable than bipolar junction transistors and control the amount of current by the voltage signal. JFETs are broken down into two basic configurations

  • N-Channel JFET: the current flowing through the channel between the drain and source is negative in the form of electrons. It has lower resistance than P-Channel types.
  • P-Channel JFET- the current flowing through the channel is positive and has higher resistance than N-Channel JFETs.

MOSFET is a four-terminal semiconductor field effect transistor fabricated by the controlled oxidation of silicon and where the applied voltage determines the electrical conductivity of a device. In a MOSFET, the gate located between the source and drain channels is electrically insulated from the channel by a thin layer of metal oxide to control the voltage and current flow between the source and drain channels. MOSFETs are used in integrated circuits because of their high input impedance. They are mostly used in power amplifiers and switches, and in embedded system designs.

MOSFETs come in two configurations:

  • Depletion Mode MOSFET: the device is normally ON when the gate-to-source voltage is zero. The application voltage is lower than the drain-to-source voltage.
  • Enhancement Mode MOSFET- the device is normally OFF when the gate-to-source voltage is zero.

Comparing the two, JFETs are easier to manufacture and are less expensive. They are also less susceptible to damage because of their high input capacitance. MOSFETs are able to operate in high noise applications, and can operate in both depletion and enhancement mode, and have a higher input impedance.               

At ASAP NSN Hub, owned and operated by ASAP Semiconductor, we can help you find all the electrical transistors for the aerospace, civil aviation, and defense industries. For a quick and competitive quote, email us at sales@asapnsnhub.com or call us at 1-920-785-6790.


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