A MOSFET transistor is essentially a FET (Field Effect Transistor) transistor with an insulated gate. Meaning that it has source, gate, and drain terminals like a FET transistor, but the gate on a MOSFET transistor is insulated from the channel by a thin layer of Metal Oxide (MOSFET's sometimes may have a fourth terminal called the body but it's most commonly connected to the source terminal). The main function of a MOSFET transistor is switching or amplifying signals. The conductivity of this device is entirely controlled by the input voltage, so a change in the voltage is used to trigger the transistor to switch signals or amplify a signal. A MOSFET transistor is the most commonly used transistor in digital and analog circuits alike.
A MOSFET transistor can function in two of the following ways:
Depletion Mode – If the gate doesn’t have any voltage going to it, then the channel is at max conductance. If you put a voltage on the gate, then the channel’s conductivity will decrease with the amount of voltage applied. The depletion mode in a MOSFET transistor is equivalent to a “Normally Closed” switch.
Enhancement Mode – This mode is the exact opposite of the depletion mode. If the gate doesn’t have any voltage going to it then the channel is not conductive. The more voltage going to the gate the higher the conductivity of the channel. The enhancement mode in a MOSFET transistor is equivalent to a “Normally Open” switch.
An N-Channel MOSFET has the source connected to the ground, and the drain to the load. When you apply a positive voltage to the gate the FET will turn on. In general N-Channel MOSFETS are cheaper compared to P-Channel equivalents because they are easier to manufacturer. A P-Channel MOSFET has a positive voltage connected to the source and the FET only turns on when the voltage dips down by the desired amount.
Note: To use a P-Channel MOSFET to switch voltages higher than 5 volts, you’re going to need to add a transistor into the circuit to turn the MOSFET on and off.
|Part Number||Drain-Source Voltage
|Continuous Drain Current
|Body Type||RohS Compliance||Channel|
The TO-263 package type was designed for surface mounting onto printed circuit boards. With the leads bent back this package type can be mounted to sit flush with its mounting surface.
The TO-220 package was designed for through the hole applications. The extended tab design gives this package type the ability to be mounted to an external heat sink making it suitable for high powered applications.