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Compared to the other power semiconductor devices , such as an insulated-gate bipolar transistor IGBT or a thyristor , its main advantages are high switching speed and good efficiency at low voltages. It shares with the IGBT an isolated gate that makes it easy to drive. They can be subject to low gain, sometimes to a degree that the gate voltage needs to be higher than the voltage under control. The power MOSFET is the most common power semiconductor device in the world, due to its low gate drive power, fast switching speed,  easy advanced paralleling capability,   wide bandwidth, ruggedness, easy drive, simple biasing, ease of application, and ease of repair.
It can be found in a wide range of applications, such as most power supplies , DC-to-DC converters , low-voltage motor controllers , and many other applications.
It was a breakthrough in power electronics. Generations of MOSFETs enabled power designers to achieve performance and density levels not possible with bipolar transistors. Tarui, Y. It is used in various radio and RF applications. The cross section of a VDMOS see figure 1 shows the "verticality" of the device: it can be seen that the source electrode is placed over the drain, resulting in a current mainly vertical when the transistor is in the on-state.
In a planar structure, the current and breakdown voltage ratings are both functions of the channel dimensions respectively width and length of the channel , resulting in inefficient use of the "silicon real estate". With a vertical structure, the voltage rating of the transistor is a function of the doping and thickness of the N epitaxial layer see cross section , while the current rating is a function of the channel width.
This makes it possible for the transistor to sustain both high blocking voltage and high current within a compact piece of silicon. They are mainly used in high-end audio power amplifiers ,  and RF power amplifiers in wireless cellular networks , such as 2G , 3G ,  and 4G. It can be seen in figure 2 that this resistance called R DSon for "drain to source resistance in on-state" is the sum of many elementary contributions:.
When this highly non-symmetrical structure is reverse-biased, the space-charge region extends principally on the light-doped side, i. The thicker the layer and the lower its doping level, the higher the breakdown voltage. However, if it were, this would result in a floating P zone between the N-doped source and drain, which is equivalent to a NPN transistor with a non-connected base.
Under certain conditions under high drain current, when the on-state drain to source voltage is in the order of some volts , this parasitic NPN transistor would be triggered, making the MOSFET uncontrollable. The connection of the P implantation to the source metallization shorts the base of the parasitic transistor to its emitter the source of the MOSFET and thus prevents spurious latching. This solution, however, creates a diode between the drain cathode and the source anode of the MOSFET, making it able to block current in only one direction.
Body diodes may be utilized as freewheeling diodes for inductive loads in configurations such as H bridge or half bridge. While these diodes usually have rather high forward voltage drop, they can handle large currents and are sufficient in many applications, reducing part count, and thus, device cost and board space.
Indeed, there is no need to remove minority carriers as with bipolar devices. These capacitances must be charged or discharged when the transistor switches. This can be a relatively slow process because the current that flows through the gate capacitances is limited by the external driver circuit. This circuit will actually dictate the commutation speed of the transistor assuming the power circuit has sufficiently low inductance.
In the MOSFET datasheets , the capacitances are often named C iss input capacitance, drain and source terminal shorted , C oss output capacitance, gate and source shorted , and C rss reverse transfer capacitance, source connected to ground. The relationship between these capacitances and those described below is:.
Manufacturers prefer to quote C iss , C oss and C rss because they can be directly measured on the transistor. C oxm is the capacitance between the polysilicon gate and the metal source electrode, so it is also constant.
Therefore, it is common practice to consider C GS as a constant capacitance, i. The C GD capacitance can be seen as the connection in series of two elementary capacitances. The first one is the oxide capacitance C oxD , constituted by the gate electrode, the silicon dioxide and the top of the N epitaxial layer.
It has a constant value. Therefore, it is dependent upon the drain to source voltage. From this, the value of C GD is:. The width of the space-charge region is given by .
The value of C GDj can be approximated using the expression of the plane capacitor :. As this voltage increases, the capacitance decreases.
As the source metallization overlaps the P-wells see figure 1 , the drain and source terminals are separated by a P-N junction. Therefore, C DS is the junction capacitance. This is a non-linear capacitance, and its value can be calculated using the same equation as for C GDj.
To operate, the MOSFET must be connected to the external circuit, most of the time using wire bonding although alternative techniques are investigated. These connections exhibit a parasitic inductance, which is in no way specific to the MOSFET technology, but has important effects because of the high commutation speeds. Parasitic inductances tend to maintain their current constant and generate overvoltage during the transistor turn off, resulting in increasing commutation losses.
They have different effects:. To deal with this issue, a gate driver circuit is often used. Exceeding the breakdown voltage causes the device to conduct, potentially damaging it and other circuit elements due to excessive power dissipation. The drain current must generally stay below a certain specified value maximum continuous drain current.
It can reach higher values for very short durations of time maximum pulsed drain current, sometimes specified for various pulse durations. The drain current is limited by heating due to resistive losses in internal components such as bond wires , and other phenomena such as electromigration in the metal layer. The packaging often limits the maximum junction temperature, due to the molding compound and where used epoxy characteristics. The maximum operating ambient temperature is determined by the power dissipation and thermal resistance.
The type of power dissipation, whether continuous or pulsed, affects the maximum operating temperature , due to thermal mass characteristics; in general, the lower the frequency of pulses for a given power dissipation, the higher maximum operating ambient temperature, due to allowing a longer interval for the device to cool down. Models, such as a Foster network , can be used to analyze temperature dynamics from power transients.
The safe operating area defines the combined ranges of drain current and drain to source voltage the power MOSFET is able to handle without damage. It is represented graphically as an area in the plane defined by these two parameters. Both drain current and drain-to-source voltage must stay below their respective maximum values, but their product must also stay below the maximum power dissipation the device is able to handle.
Thus, the device cannot be operated at its maximum current and maximum voltage simultaneously. This phenomenon is known as " latch-up ", which can lead to device destruction. The BJT can be turned on due to a voltage drop across the p-type body region. To avoid latch-up, the body and the source are typically short-circuited within the device package. The gate channel width is the third Z-axis dimension of the cross-sections pictured.
To minimize cost and size, it is valuable to keep the transistor's die area size as small as possible. Therefore, optimizations have been developed to increase the width of the channel surface area, i. Another way to increase the channel density is to reduce the size of the elementary structure.
This allows for more cells in a given surface area, and therefore more channel width. However, as the cell size shrinks, it becomes more difficult to ensure proper contact of every cell.
To overcome this, a "strip" structure is often used see figure. It is less efficient than a cellular structure of equivalent resolution in terms of channel density, but can cope with smaller pitch. Another advantage of the planar stripe structure is that it is less susceptible to failure during avalanche breakdown events in which the parasitic bipolar transistor turns on from sufficient forward bias. In the cellular structure, if the source terminal of any one cell is poorly contacted, then it becomes much more likely that the parasitic bipolar transistor latches on during an avalanche breakdown event.
Because of this, MOSFETs utilizing a planar stripe structure can only fail during avalanche breakdown due to extreme thermal stress. As the channel sits in a N-region, this transistor is turned on by a negative gate to source voltage. The main disadvantage of this type of MOSFET is the poor on-state performance, as it uses holes as charge carriers , which have a much lower mobility than electrons.
This results in a vertical channel. The main interest of the structure is the absence of the JFET effect. The name of the structure comes from the U-shape of the trench. Seeking to improve the manufacturing efficiency and reliability of super-junction MOSFETs, Renesas Electronics developed a super-junction structure with a deep-trench process technique.
This technology entails etching trenches in the low-impurity N-type material to form P-type regions. This process overcomes problems inherent to the multi-level epitaxial growth approach and results in extremely low on-resistance and reduced internal capacitance.
Due to the increased p-n junction area, a super-junction structure has a smaller reverse recovery time but larger reverse recovery current compared to a conventional planar power MOSFET. From Wikipedia, the free encyclopedia.
David The Industrial Electronics Handbook. CRC Press. Retrieved 29 July High Performance Audio Power Amplifiers. Electronic Design. Retrieved 23 July Fet Technology and Application. Power Electronics Technology. Informa : 52—6. September Archived PDF from the original on 22 March Retrieved 31 July Proceedings of the 1st Conference on Solid State Devices.
IRF MOSFET Power Transistors
Compared to the other power semiconductor devices , such as an insulated-gate bipolar transistor IGBT or a thyristor , its main advantages are high switching speed and good efficiency at low voltages. It shares with the IGBT an isolated gate that makes it easy to drive. They can be subject to low gain, sometimes to a degree that the gate voltage needs to be higher than the voltage under control. The power MOSFET is the most common power semiconductor device in the world, due to its low gate drive power, fast switching speed,  easy advanced paralleling capability,   wide bandwidth, ruggedness, easy drive, simple biasing, ease of application, and ease of repair. It can be found in a wide range of applications, such as most power supplies , DC-to-DC converters , low-voltage motor controllers , and many other applications. It was a breakthrough in power electronics. Generations of MOSFETs enabled power designers to achieve performance and density levels not possible with bipolar transistors.
IRFP250N Transistor. Datasheet pdf. Equivalent
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