EducationTransil Diode / TVS - Definition, Basics and Application

Transil Diode / TVS – Definition, Basics and Application

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Transil Diode / TVS

Transil Diode (Transient Voltage Suppressor, TVS) – the type of protecting semiconductor diode with method of operation similar 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 secure single components e.g. transistors. Transil Diodes are used e.g. in medical electronic devices, computers, printers, and wireless communication systems.

transil symbols
Fig. 1. Transil symbol: a) unidirectional, b) bidirectional

Transil Diode – Example of simple securing system

transil diode securing system
Fig. 2. Schematic of the TVS securing system

After exceeding the avalanche breakdown threshold 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 very short period of time. It is also characterised by short response time (measured in picoseconds), therefore it’s such a good protection component.

Transil Diode – Technical parameters (model SM6T)

  • PPPD – Peak Pulse Power Dissipation: 600W,
  • VBR – breakdown Voltage : 6.8 to 220V,
  • Polarization,
  • Tjmax – maximum operating junction temperature: 150°C.


Michal Pukala
Electronics and Telecommunications engineer with Electro-energetics Master degree graduation. Lightning designer experienced engineer. Currently working in IT industry.



  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.