Transient voltage suppressor (TVS) diodes are semiconductor devices that are used to protect electronic circuits from transient voltage spikes such as electrostatic discharge (ESD), inductive load switching, and induced lightning strikes. TVS diodes act as variable resistors, allowing normal current to pass but clamping at a predetermined voltage level during transient events. This protects internal circuitry from being damaged by high voltage surges.

Construction and Working Principle

TVS diodes contain a PN junction fabricated from semiconductor materials with a low breakdown voltage such as silicon or germanium. Unlike normal rectifier diodes, TVS diodes have a special doping profile that results in a gradual breakdown under increasing voltage rather than a hard switch. When a transient voltage spike exceeds the Transient Voltage Suppressor Diode clamping voltage, the diode becomes momentarily conductive which provides a path to quickly discharge the excess energy harmlessly to ground. This action effectively limits the peak voltage applied to the protected circuit. After the transient passes, the TVS diode returns to its high-impedance state.

Types of Transient Voltage Suppressor Diode

There are different types of TVS diodes available to suit various protection requirements:

- Unidirectional TVS diodes only block voltages in one direction and are commonly used as input protection on lines that normally carry voltage in just one polarity.

- Bidirectional TVS diodes can block voltages in both polarities and are useful for lines that may experience transients of either positive or negative polarity.

- Low capacitance TVS diodes have minimized stray capacitance for higher frequency/faster transient protection with less signal distortion.

- High-energy TVS diodes are able to absorb more energy from large transient events such asindirect lightning strikes without damage.

Parameter Considerations

Some key parameters to consider when selecting a TVS diode include:

Clamping voltage: The maximum steady-state or repetitive voltage the device can withstand before conduction begins.

Maximum peak pulse current: The highest non-repetitive surge current the TVS can handle without failure.

Capacitance: The amount of stored charge available. Lower capacitance TVS diodes provide faster response times.

Response time: The switching speed from non-conducting to conducting state during a transient. Faster devices have lower response times.

Power dissipation: The maximum power the TVS can safely dissipate during a transient without overheating.

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