1SMA4742-GT3TR

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Diodes - Zener - Single

The 1SMA4742-GT3TR is a single Zener diode, and it is in a SMA (Surface Mount Application) package. It offers a maximum reverse voltage (Vr) of 45 volts, with a maximum power dissipation of 250 milliwatts. The maximum forward current (If) is 1.5 amperes and the forward voltage (Vf) is 0.9 volts. The junction temperature (Tj) is -55 to +175 degrees Celsius. It is a low capacitance diode suitable for use in computer and telecoms applications.

Applications

The 1SMA4742-GT3TR operates in many different applications. It is widely used in the Telecom and Data Communication markets, particularly across large area networks, where high-speed data transmission (e.g. 1 Gbps Ethernet) requires low capacitance and low loss. This diode is also used in high-frequency switching circuits, such as in amplifier, detector and oscillator circuits in RF and microwave applications.

The 1SMA4742-GT3TR is used in automotive applications, such as in reverse polarity protection, where it will allow current to flow in either direction without becoming damaged, and DC-DC converters, where it helps regulate the voltage passed from one circuit to another. It can also be used in amplifier circuitry, rectification and modulation applications, where it provides the necessary steps for the transfer of energy.

Working Principle

Zener diodes are diodes that are designed to allow the backflow of current, unlike regular diodes which are PN junctions that prevent voltage flow in the reverse direction. The 1SMA4742-GT3TR works on the principle of a Zener effect, which occurs when the PN junction of a diode experiences a breakdown at a specific reverse voltage. During this breakdown, the diode conducts current in the reverse direction, allowing current to flow from anode to cathode.

The operation of the 1SMA4742-GT3TR is "specifically designed for low capacitance applications, allowing up to 45V reverse voltage with low capacitance and minimal circuitry changes. The Zener diode exhibits a predictable output, even with a proportionately small current overdrive, making it suitable for applications requiring very reliable circuit design. In addition, it is also designed to withstand high temperatures, which makes it suitable for operations in harsh environments."

At a reverse voltage higher than the Zener voltages of the diode, the diode operates in a reverse-bias mode. In this mode, the diode only passes current through it in an insignificant amount known as the "Zener Breakdown", which is determined by temperature, capacitance, and breakdown voltage.

The 1SMA4742-GT3TR then passes through the “avalanche region of operation.” At this point, current flows and the Zener diode begins to act more like a resistor and less like a PN junction diode. The current then passes through the diode and then out of it, allowing current to flow in both directions.

Conclusion

The 1SMA4742-GT3TR is a single Zener diode, offering a maximum reverse voltage of 45 volts, with a maximum power dissipation of 250 milliwatts. It offers a low capacitance that is suitable for use in computer and telecoms applications. It is widely used in the Telecom and Data Communication markets, as well as high-frequency switching circuits, automotive applications, and amplifier and modulation circuits. The diode works on the principle of a Zener effect and exhibits a predictable output, even with a proportionately small current overdrive, making it suitable for applications requiring very reliable circuit design.

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