Transistor IRFZ44N: Pinout, Circuit Diagram & Equivalent

Today we will take a detailed look at the IRFZ44N transistor’s specifications, pinout, wiring diagram and equivalents for replacement. It is a silicon based power device with induced n-channel (normally closed) isolated gate. It is characterized by drain-to-drain voltages up to 55 V, drain current up to 49 A, very small bore resistance of 17.5 mOhm and power dissipation up to 94 W. Operating temperatures can be as high as 175 °C. Designed specifically for low-voltage, high-speed switching systems of power supplies, converters, and motor controls.

Graphic designation

Let’s look at the graphic notation. The type-n channel is drawn with a dotted line, between the source and drain lines adjacent to it. The arrow pointing to the dotted line indicates the electronic conductivity of the device. Channel leads are designated by letters: C-drain (D-drain), I-source (S-source). The gate, which regulates the channel resistance, is designated by the letter Z (G-gate). There is a so-called “parasite” diode in the designation, it is connected to the source with the anode. All the graphic symbols are placed in a circle, symbolizing the body of the device.

The pinout

The most widespread rfz44n was in the plastic package TO220 with a screw fixing hole, developed specially for discrete power field effect transistors by International Rectifier. The pin assignment of irfz44n, when looking at the front side, is as follows: gate (G) on the left, source (S) on the right. The middle pin is the drain (D), electrically connected to the built-in heat sink. Under the International Rectifier brand there are examples in D2PAK and TO-262 (irfz44ns, irfz44nl) packages, pin assignment is similar to TO-22.


Basic Specifications

The entire list of MOSFET transistor parameters is not even specified in the datasheet, as only professional developers would need it. But even experienced designers usually only need to know some basic values to start using the device in their electronic circuits. The IRFZ44N is characterized by the following basic parameters (at temperatures up to +25 degrees):

  • The maximum drain-source voltage (V DSS) is 55 V;
  • Maximum drain current (I D) – 49 A;
  • Drain channel resistance (R DSon) – 5 mOhm;
  • Power dissipation (P D) – 94 W

In some technical descriptions, the name of a MOS (or mosfet) gate-insulated transistor may begin with the acronym TIR. MDM is the first letters of the words metal, dielectric, and semiconductor. These transistors are subdivided into induced-channel and embedded-channel devices. These semiconductor devices have a gate separated from the silicon substrate by the thinnest dielectric layer (approximately 0.1 micrometer).

Maximum values

Usually, the maximum permissible values are stated at the beginning of the datasheet. In them, the manufacturer writes information about the limits of the operation of radio components, at which they can work. The device is tested at ambient temperatures of up to 25 degrees, unless the manufacturer specifies otherwise. Having only studied these parameters, you can already make a decision about their use in your circuits. For example, about the possibility of application in different temperature regimes. For example, the MOSFET in question can drop from 49A to 35A when the ambient temperature increases to 100°C.


Thermal parameters

It is no secret that the performance of a power MOSFET is highly dependent on how well it dissipates heat. To simplify calculations related to heat dissipation, thermal resistance parameters are introduced. Their values show the ability of radio components to limit the spread of heat. The greater the thermal resistance, the faster the temperature of the semiconductor device will increase. Thus, the greater the difference between the limiting temperature of the crystal and the external environment, the longer its heating time, and the higher the current transmitted. The instance in question has the following thermal resistances.


Electrical parameters              

It is clear that the power and passing currents between the contacts should not exceed the maximum values declared by the manufacturer. At the same time, there are other factors that can cause a sharp increase in temperature, contributing to the destruction of the semiconductor. Therefore, manufacturers advise choosing devices with a 20-30% margin on possible applied voltage levels, and the datasheet provides the rated electrical specifications. For the IRFZ44N, the electrical specs, at Tj=25°C (unless otherwise specified) are given below.



The prefix IRF is a reminder of the origin of the specimen in the factories of the famous American company International Rectifier (IR). In 2007, IR sold MOSF technology to Vishay Intertechnology, and in 2015 another company (Infineon Technologies) took over IR. Currently, many independent manufacturers continue to produce their products with the prefix IRF, so in the market of modern radio components you can find other manufacturers producing products with the same symbols in the designation. For example Vishay, which no longer manufactures irfz44n transistors, but has other similar devices such as IRFZ44, IRFZ44R, IRFZ44S, IRFZ44SL.

In some data sheets, “PbF” is indicated at the end of the marking, e.g. IRFZ44NPbF. PbF (plumbum free) – it is a lead free MOSFET technology which is gaining popularity in various countries due to the ban on the use of substances hazardous to health and the environment in electronics.

The datasheet of the original device specifies the presence of proprietary HEXFET-manufacturing technology from International Rectifier Corporation, which can significantly reduce the resistance of electronic components and thus reduce heating during their operation. It also eliminates the need for a cooling radiator. The technology became popular in 1978, but it is still used in the manufacture of power MOSFETs. A simplified HEXFET structure of International Rectifier is shown in the figure.


IRFZ44N manufactured with HEXFET structure has the lowest drain-to-source resistance of 17.5 milliom. The designation “Power MOSFET” in the datasheet indicates that the device belongs to high-power semiconductors.


There are no complete equivalents for irfz44n, but there are very similar MOSFETs in terms of their specifications and description. These include IRFZ44E, IRFZ45, IRFZ46N, IRFZ40, BUZ102, STP45NF06, IRLZ44Z, HUF75329P3, IRF3205. Domestic analogues are KP723 and KP812A1, although their operating temperature is a bit lower (up to 150°C).

Switching circuit

As said above it is a field effect transistor-MOSF with gate separated from semiconductor by very thin SiO2 layer. There are two p-n junctions inside the silicon structure. If no opener voltage is applied, there is no conducting current and the transistor is in a closed state. If a positive VGS is applied to the device, i.e., plus to the gate and minus to the source, an induced n-conductivity channel will appear under the influence of the electric field. When power is applied to the load, the induced channel will carry the drain current ID.


The higher the voltage applied to the gate, the more electrons are attracted to the drain-source region and the wider it becomes for current to flow. However, this process can last until it switches between the linear and cutoff regions of the graph. Then, in the saturation region, the drain current stops growing. The saturation region (operating mode) is used in gain circuits, and the cutoff region in key circuits. In the datasheet, the transition to the operating mode, for different values of VGS, is shown in the Typical Output Specifications graphs. For a mosfet, the saturation area can be determined by a line that runs almost horizontally with respect to the drain-source voltage axis.



The irfz44n field-effect transistor is very popular with radio amateurs in various electronic single transistor amplification circuits, sensor switches, motor speed controllers, arduino projects, etc. It can often be seen in high-frequency switching power supplies, generators, stabilizers, inverters and power load connection circuits. Here is a video with some interesting ideas from this great semiconductor device.


Below is a technical description of the following manufacturers of radioelectronic components:

  • Infineon Technologies (International Rectifier brand);
  • Philips Semiconductors;
  • INCHANGE Semiconductor;
  • Leshan Radio Company.
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