Overview

BT137 and BTA08 are both bidirectional TRIACs, but they differ in parameters, packaging and application scenarios.Here’s a comparison:

Parameters Comparison

ParameterBT137BTA08
Current Rating8A (RMS)8A (RMS)
Voltage Rating600V/800V (e.g., BT137-600)600V/800V (e.g., BTA08-600)
Trigger Current~5mA (typical)~10–50mA (less sensitive)
PackageTO-220C (non-insulated, requires isolation)TO-220AB(fully insulated) 
On-State Voltage Drop~1.6V (typical)~1.5V (typical)

Key Differences

  • Package & Isolation
    BT137: TO-220C package,requires an insulating pad when mounted on a heatsink.
    BTA08: TO-220A package,available in insulated packages,no extra insulation is needed for heatsink mounting.
  • Trigger Sensitivity
    BT137: Lower gate trigger current (~5mA), making it easier to drive directly from low-power circuits.
    BTA08: Higher trigger current (typically 10–50mA), requiring a stronger gate drive.
  • Heat Dissipation
    BT137: Requires an insulating pad, which can slightly reduce thermal efficiency.
    BTA08 (insulated models): No insulation needed, but plastic packaging may limit heat dissipation compared to metal tabs.
  • Typical Applications
    BT137: Used in low-power AC control (e.g., dimmers, small motor controls, household appliances).
    BTA08: Preferred for industrial applications (e.g., heaters, high-power switching) due to its ruggedness and insulated options.

Interchangeability

If voltage/current ratings match (e.g., 600V/8A), they can be substituted, but consider:

  • Replacing BT137 with BTA08: Ensure the gate drive circuit can supply enough trigger current.
  • Replacing BTA08 with BT137: Add an insulating pad if the heatsink is grounded.

Selection Guide

  • Choose BT137 for cost-sensitive, low-power designs with simple triggering.
  • Choose BTA08 for industrial or safety-critical applications where insulation is required.