HT34B

Overview

The Littelfuse HT34B is a standard bidirectional DIAC trigger thyristor belonging to the HTxxx series. It operates within a breakover voltage range of 32V (minimum) to 36V (maximum). The device supports a pulse on-state current of 1.5A at 120 pulses per second with a junction temperature not exceeding 40°C. It features a DO-35 glass case package and is RoHS compliant. The component functions by triggering from a blocking state to conduction when applied voltage exceeds its breakover threshold for either polarity.

Feature Summary

• Bidirectional switching capability for full-wave phase control applications
• High reliability through glass-passivated junctions resistant to contamination
• RoHS compliant construction utilizing lead-free solder dipping

Applications

• Lamp dimming circuits
• Universal motor speed control systems
• Heat control applications
• Solid state ballast lighting controls

Procurement Notes

Verify the specific ordering suffix against the manufacturer's datasheet to confirm the exact package type, as the HT34B designation corresponds to the DO-35 leaded variant. Confirm that the required breakover voltage symmetry meets the application tolerance, noting that tighter symmetry specifications may require factory selection or alternative part numbers within the same series.

Selection Notes

Select the HT34B when a breakover voltage between 32V and 36V is required for AC phase control. Ensure the circuit design accommodates the 1.5A pulse on-state current limit at 120 pps. Consider thermal derating factors if the ambient operating temperature exceeds 40°C, as power dissipation capabilities decrease above this threshold according to the specified junction-to-lead thermal resistance values.

Part Context

The HT34B is part of the broader HTxxx & HTMxxx & STxxx Series of Standard Bidirectional DIAC Triggers manufactured by Littelfuse under the Teccor brand. This family offers various breakover voltages ranging from 27V to 70V across different package styles including MINIMELF, DO-35, and DO-214. These devices are designed specifically for triggering Triacs and SCRs in industrial and consumer electronics.

Replacement Considerations

Direct replacements include other HT-series DIACs with matching voltage ranges, such as HT-32B or HT-35, provided the breakover voltage characteristics align with the circuit requirements. Alternative packages like ST-34B (DO-214) offer equivalent electrical performance but require surface mount layout adjustments.