New Industry Products

STMicroelectronics Introduces a Line of 800V Snubberless Triacs

January 21, 2021 by Gary Elinoff

The new units operate at their full rated currents at junction temperatures of up to 150ºC

STMicroelectronics’ 8H triacs’ high heat tolerances allow for heat sinks sized as much as 50% smaller when driving AC loads. Members of the new family have current carrying capacities ranging from 8 to 30 amps


STMicroelectronics Introduces a line of 800V, Snubberless Triacs Figure
Image courtesy of STMicroelectronics


What is a Triac?

A Triac is a three terminal semiconductor device. Much like a classical electromechanical relay, it functions as a switch, with a small input signal applied at the device’s “gate” controlling the conduction of much greater voltage and current across its two output terminals. 

Unlike most mechanical relays, even after the small input signal is removed, the triac continues to carry the power. Once the power is no longer present at the triac’s output, it takes another pulse at the gate to drive the device again into conduction.

The equivalent circuit of a triac is two SCRs joined back-to-back.


STMicroelectronics Introduces a line of 800V, Snubberless Triacs Figure
Image courtesy of All About Circuits


The two “SCRs” are turned on simultaneously, with one poised to carry current in one dimension, the other in the opposite direction. Thus, the device can switch AC as well as DC

Triacs are silicon semiconductor devices. As such, they generate no sparks, which is an enormous advantage in industrial environments where equipment may be operating in presence of flammable gasses. This is a key advantage over mechanical relays


Snubberless Triac 

Because a large amount of power is being turned on and turned off, sometimes at great speed, significant EMI can be generated. A snubber is a means to ameliorate the EMI, and some triacs incorporate that capability internally. Those that do not are referred to as snubberless triacs.


Applicable for 3-Phase Equipment

The members of the 8H family are capable of driving inductive loads. Additionally, their peak off-state voltages of 800 volts make them suitable for deployment with 3-phase equipment operating at voltages of up to 400 VRMS.

The new triacs feature low on-state voltages (VTM); the maximum voltage drop across the terminals when the devices are conducting.

The snubberless devices themselves exhibit high immunity to noise. They can tolerate fast transients as high as 6 kV and voltage gradients as high as 2000 volts per microsecond at junction temperature within spec.



There are a total of 15 members of the family and are available in a ceramic-insulated TO-220AB package, D2PAK or classical TO-220AB packages. The reader can select “View all 800V 8H Triacs products”,  found on this page, for a complete listing. 

For a typical part number, T3035H-8T, the “30” after the “T” indicates that it can handle 30 amps. If the very last two character sequence in the part number is “8G”, that indicates a D2PAK package. “8T” indicates 220AB, and “8I” indicates T0220AB insulated  


Applications include:

  • HVAC systems
  • AC-motor drives
  • Water heaters
  • Industrial applications
  • Home appliances
  • Room heaters
  • Smart AC plugs.
  • Lighting systems
  • Smart home and smart building



The units are ECOPACK2 compliant. This standard covers RoHS, REACH and ELV

The molding resin for the series is UL94-V0 flammability certified.