Littelfuse Q4008R4 TRIAC 400V 8A TO-220 Equivalent & Substitute Parts

Part Overview

The Littelfuse Q4008R4 is a standard TRIAC rated for 400V off-state voltage and 8A on-state current in a TO-220-3 through-hole package. This component is discontinued at DiGi Electronics, making equivalent substitute parts necessary for ongoing design requirements and production continuity. The part is ROHS3 compliant with unlimited moisture sensitivity level (MSL 1).

Substiute Parts

Q4008R4

LittelfuseIn Stock: 874Q4008R4 Datasheet

Current PartRFQ

BT138-600E,127

WeEn SemiconductorsIn Stock: 1114BT138-600E,127 Datasheet

MFR RecommendedRFQ

BTA08-400BRG

STMicroelectronicsIn Stock: 3733BTA08-400BRG Datasheet

MFR RecommendedRFQ

BTB08-600CRG

STMicroelectronicsIn Stock: 1892BTB08-600CRG Datasheet

MFR RecommendedRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitute parts for the Q4008R4 are selected based on the following critical parameters:

Primary Matching Criteria:

• Off-state voltage rating of 400V or higher
• On-state current rating of 8A or higher
• Gate trigger voltage (Vgt) of 1.3V or lower
• TO-220-3 package configuration
• Through-hole mounting type
• Standard or Logic-Sensitive Gate TRIAC type

Acceptable Substitution Logic: Parts with equal or higher voltage ratings and equal or higher current ratings maintain or exceed the original design margins. Gate trigger voltage specifications at or below the original value ensure compatible gate drive requirements. All substitute parts maintain the same package and mounting configuration for direct mechanical and electrical interchange.

Parameter Comparison

Engineering Selection Recommendations

BTA08-400BRG (STMicroelectronics) provides the closest electrical match to the Q4008R4, with identical voltage and current ratings, matching gate trigger voltage, and equivalent operating temperature range. This part is currently active in production with ROHS3 compliance and REACH unaffected status.

BTB08-600CRG (STMicroelectronics) offers increased voltage margin at 600V while maintaining 8A current rating and 1.3V gate trigger voltage. This part is active with full compliance certifications and provides enhanced overvoltage protection for the same current class.

BT138-600E,127 (WeEn Semiconductors) features a Logic-Sensitive Gate configuration with reduced gate trigger current (10mA versus 25mA), higher current rating (12A), and 600V voltage rating. This part is active and ROHS3 compliant. The sensitive gate characteristic reduces gate drive requirements compared to standard TRIAC types.

All three substitute parts maintain TO-220-3 through-hole packaging, ROHS3 compliance, and MSL 1 moisture sensitivity level, ensuring direct compatibility with existing PCB designs and assembly processes.

Frequently Asked Questions (FAQ)

Q: Can BTA08-400BRG directly replace Q4008R4 in existing designs? A: Yes. BTA08-400BRG matches the Q4008R4 in voltage rating (400V), current rating (8A), gate trigger voltage (1.3V), and operating temperature range (-40°C to 125°C). Both are standard TRIAC types in TO-220-3 packages. The primary difference is gate trigger current specification (50mA versus 25mA), which requires verification that gate drive circuitry can supply the higher current.

Q: What is the advantage of BTB08-600CRG over BTA08-400BRG? A: BTB08-600CRG provides 600V off-state voltage rating compared to 400V, offering increased margin for transient overvoltage conditions. Both maintain 8A current rating and 1.3V gate trigger voltage. Selection depends on application voltage stress requirements.

Q: Why does BT138-600E,127 have different gate trigger current specifications? A: BT138-600E,127 is a Logic-Sensitive Gate TRIAC type, which by design requires lower gate trigger current (10mA) compared to standard TRIAC types. This characteristic reduces gate drive power requirements but requires gate drive circuitry compatible with sensitive gate operation.

Q: Are all substitute parts available in the same package configuration? A: Yes. All substitute parts use TO-220-3 through-hole packages with identical pin configurations, enabling direct mechanical and thermal interface compatibility with existing PCB designs.

Q: Do all substitute parts meet the same compliance requirements? A: All substitute parts are ROHS3 compliant with MSL 1 moisture sensitivity level. BTA08-400BRG and BTB08-600CRG have REACH unaffected status. BT138-600E,127 does not list REACH status in available specifications.