HT40

Overview

The Littelfuse HT40 is a standard bidirectional DIAC trigger device belonging to the HTxxx series. It operates as a full-wave semiconductor switch, transitioning from a blocking state to conduction when applied voltage exceeds its breakover threshold for either polarity. The component features glass-passivated junctions and is housed in a DO-35 package. Electrical characteristics include a minimum breakover voltage of 35V and a maximum of 45V at 25°C. It supports a pulse on-state current of 1.5A (HT-60 specific limit applies to other models) and maintains an operating junction temperature range from -40°C to +125°C.

Feature Summary

• Bidirectional triggering capability for AC phase control applications
• Glass-passivated junctions ensuring long-term parameter stability
• DO-35 axial leaded package construction

Applications

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

Procurement Notes

Verify the exact part number suffix against the manufacturer's selector table to confirm the specific voltage tolerance class and packaging format. Ensure the selected variant matches the required thermal dissipation limits for the intended ambient temperature conditions. Confirm compliance with RoHS standards if applicable to the assembly process.

Selection Notes

Select the HT40 based on the required breakover voltage symmetry and peak current handling capabilities. Consider the thermal resistance values for the DO-35 package when designing heat dissipation strategies. Verify that the application circuit provides adequate current limiting to prevent damage during the transition from blocking to conducting states.

Part Context

The HT40 is part of the Teccor brand Thyristors family, specifically the HTxxx & HTMxxx & STxxx Series of Standard Bidirectional DIAC Triggers. This series offers a range of voltage characteristics from 27V to 70V. The HT40 specifically targets applications requiring a 35V to 45V breakover range within this broader product line.

Replacement Considerations

Compatible substitutes include HT-32, HT-34B, HT-35, HT-36A, HT-36B, and HT-60 variants within the same series. Selection depends on matching the specific breakover voltage window and package type requirements.