transil diode securring system

Transil Diode – Definition, symbol and basics


Transil Diode

Transil Diode (Transient Voltage Suppressor, TVS) – the type of protecting semiconductor diode with the similar operating method to varistor, which is designed to protect sensitive electronic components from electrical surges. We distinguish unidirectional and bidirectional TVSs. The first one is used to protect the entire circuit, the other one is used to e.g. secure transistors.

transil symbols

Transil symbol: a) unidirectional, b) bidirectional

Simple securing system with Transil diode used:

transil diode securring system

After exceeding the avalanche breakdown by the TVS, the current of high intensity starts flowing, which in succession blows a fuse and breaks the circuit. It can absorb the power of 600-1500W in a short period of time. It is also characterised by short response time (measured in picoseconds), therefore it’s such a good protection element.

Examples of parameters of the transient diode (model SM6T):

  • PPP – Peak Pulse Power Dissipation: 600W,
  • VBR – breakdown Voltage : 6.8 to 220V,
  • Directivity,
  • Tj max – Maximum operating junction temperature: 150°C,


Transil Diodes are used e.g. in medical equipment, computers, printers, and wireless communications systems.




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I'm Michael. Me and my friend John are students of electronics. We are creating this site to help students and any interested people understand electronics.

One thought on “Transil Diode – Definition, symbol and basics

  1. A bidirectional transient-voltage-suppression diode can be represented by two mutually opposing avalanche diodes in series with one another and connected in parallel with the circuit to be protected. While this representation is schematically accurate, physically the devices are now manufactured as a single component.

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