NXP Semiconductors BT138-800/DG,127

Overview

BT138-800/DG,127 from NXP Semiconductors is a planar passivated 4-quadrant triac in TO-220AB (SOT78) package, rated for 800 V repetitive peak off-state voltage, 12 A RMS on-state current, and 95 A non-repetitive peak on-state current at 20 ms. It operates up to 125 °C junction temperature and supports full-cycle bidirectional switching in motor control, lighting dimming, and heating systems.

For engineers reviewing the BT138-800/DG,127 datasheet, BT138-800/DG,127 pinout, BT138-800/DG,127 application, or BT138-800/DG,127 equivalent, key selection criteria include gate trigger current across all four quadrants (5–70 mA), dV/dt immunity (100–250 V/µs), thermal resistance to mounting base (1.5 K/W full cycle), on-state voltage (1.4–1.65 V @ 15 A), and latching/holding current specifications critical for reliable zero-crossing and phase-control designs.

Technical Context

The BT138-800/DG,127 implements a symmetrical four-quadrant triggering architecture enabling gate control with either polarity of main terminal voltage and gate signal - essential for universal AC phase-angle control without external polarity conditioning. Its planar passivation ensures stable blocking behavior under high dv/dt stress and thermal cycling.

It features low sensitivity to noise due to higher gate trigger thresholds in T2−/G+ quadrant (22–70 mA), while maintaining robust turn-on capability across all quadrants. The device's thermal design centers on direct heat conduction via the mounting base (T2-connected tab), with Rth(j-mb) = 1.5 K/W for full-cycle operation - optimized for heatsink-mounted industrial loads.

Key Specifications

Pinout & Package

Package: TO-220AB (SOT78), plastic single-ended package with heatsink-mounted metal tab (T2-connected), 3 leads, 1 mounting hole. Dimensions: 15.2–16.0 mm height, 9.7–10.3 mm width, 4.1–4.7 mm thickness; tab extends fully to bottom edge for mechanical stability and thermal transfer.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 4Q triac applications.

Compared with BT138-800/DG,127, the BT138-800E offers identical performance and footprint for seamless second-source flexibility, while the 2N6071A trades voltage/current capability for lower gate drive sensitivity - requiring redesign of snubbers, heatsinks, and driver stages in 230 VAC systems.

Availability

BT138-800/DG,127 is available at Aetrix Electronics and suitable for industrial motor control, residential lighting dimming, and electric heating systems requiring stable component supply, long-lifecycle support, and traceable sourcing from qualified distributors.

Supply support for BT138-800/DG,127 includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

NXP Semiconductors is a global semiconductor company headquartered in Eindhoven, Netherlands, specializing in high-performance analog, logic, and power devices for industrial, automotive, and consumer markets.

The BT138-800/DG,127 belongs to NXP's high-voltage discrete power portfolio, designed specifically for robust, thermally efficient AC power control in harsh industrial and domestic environments where reliability under thermal cycling and electrical transients is critical.

FAQ

What is the maximum junction temperature rating for BT138-800/DG,127?

The BT138-800/DG,127 has a maximum junction temperature (T_j) of 125 °C, as specified in its limiting values table. This rating applies under continuous operation with mounting base temperature ≤99 °C and proper heatsinking. Exceeding this limit risks permanent degradation of the planar passivation layer and increased leakage current. Thermal design must ensure that power dissipation - calculated from I_T(RMS)² × R_DS(on) equivalent - stays within safe margins using the documented R_th(j-mb) = 1.5 K/W value.

Does BT138-800/DG,127 support triggering in all four quadrants?

Yes, BT138-800/DG,127 is explicitly designed as a 4Q triac and supports triggering in all four quadrants: T2+/G+, T2+/G−, T2−/G−, and T2−/G+. Gate trigger current ranges from 5 mA (T2+/G+) to 70 mA (T2−/G+) at 25 °C, with normalized curves showing stable operation up to 125 °C. This enables universal AC phase-control without external polarity conditioning components, making BT138-800/DG,127 ideal for compact dimmers and motor controllers.

What is the thermal resistance from junction to mounting base for BT138-800/DG,127?

The BT138-800/DG,127 has a thermal resistance from junction to mounting base (R_th(j-mb)) of 1.5 K/W for full-cycle operation and 2.0 K/W for half-cycle operation, per its thermal characteristics table. This value assumes direct metal-to-metal contact between the TO-220AB mounting base (T2 terminal) and an adequately sized heatsink. Proper thermal interface material and mounting torque are required to achieve this specification in practice - deviations increase effective R_th and reduce allowable RMS current.

Can BT138-800/DG,127 replace BT138-600 in a 230 VAC design?

No - BT138-800/DG,127 is not a direct replacement for BT138-600 in 230 VAC applications requiring high transient margin. While both share the same package and RMS current rating, BT138-800/DG,127 provides 800 V V_DRM versus 600 V for the -600 variant. Using BT138-600 in 230 VAC systems risks premature breakdown during line surges or switching transients. BT138-800/DG,127 delivers necessary headroom; substituting the lower-voltage part compromises safety and long-term reliability.

What is the gate trigger voltage specification for BT138-800/DG,127?

The gate trigger voltage (V_GT) for BT138-800/DG,127 is specified as 0.25–0.4 V at 125 °C and 400 V off-state voltage, per its characteristics table. At 25 °C, typical V_GT is ~0.4 V, decreasing with rising temperature. This low threshold enables compatibility with standard microcontroller GPIO outputs or optocoupler drivers without level-shifting. Designers must ensure gate drive circuits deliver ≥0.5 W average power and withstand 2 A peak gate current (I_GM) to avoid damage during transient events.