NXP Semiconductors BUT12AI,127

Overview

BUT12AI,127 from NXP Semiconductors (formerly Philips) is a silicon diffused npn power transistor in TO220AB package, rated for 450 V V_CEO, 8 A DC collector current, and 110 W total power dissipation at T_hs ≤ 25 °C. It delivers 1.5 V V_CEsat at I_C = 5 A / I_B = 0.86 A and features 300 ns inductive fall time, making it suitable for high-frequency lighting ballasts and switching regulators.

For engineers reviewing the BUT12AI,127 datasheet, BUT12AI,127 pinout, BUT12AI,127 application, or BUT12AI,127 equivalent, key selection criteria include peak voltage capability (1000 V V_CESM), thermal resistance to heatsink (1.15 K/W), safe operating area under inductive switching, and verified performance at junction temperatures up to 150 °C.

Technical Context

The BUT12AI,127 is a glass-passivated npn bipolar junction transistor optimized for high-voltage, high-speed switching in off-line converters and electronic ballasts. Its design emphasizes robustness under inductive loads, with documented turn-off storage time of 1.9–2.5 µs and fall time of 150–300 ns at T_j = 100 °C, LB = 1 µH, and -V_BB = 5 V.

It operates within an absolute maximum junction temperature of 150 °C and supports base current up to 4 A DC and 6 A peak. The device exhibits h_FE = 14–35 at I_C = 1.0 A / V_CE = 5 V and h_FEsat = 5.8–12.5 at I_C = 5.0 A / V_CE = 1.5 V, enabling stable drive in hard-switched topologies.

Key Specifications

Pinout & Package

Package: TO220AB - Plastic-encapsulated power package with metal tab electrically connected to collector; requires mechanical mounting force of 30 ± 5 N and thermal interface compound for rated R_{th j-hs}.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar npn power transistor applications.

Compared with BUT12AI,127, BUT11A,127 trades voltage headroom for cost reduction in lower-stress applications, while BUX87,127 prioritizes ruggedness over speed-making BUT12AI,127 the optimal balance for high-frequency, universal-input lighting and SMPS designs.

Availability

BUT12AI,127 is available at Aetrix Electronics and suitable for electronic ballasts, switching regulators, and motor control systems requiring stable component supply and long-lifecycle support.

Supply support for BUT12AI,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 leader focused on secure connectivity solutions for automotive, industrial, and IoT markets.

The BUT12AI,127 belongs to NXP's legacy high-voltage bipolar power transistor family, engineered specifically for reliable high-frequency switching in lighting and power conversion equipment.

FAQ

What is the maximum junction temperature specification for BUT12AI,127?

The BUT12AI,127 has a maximum junction temperature (T_j) rating of 150 °C, consistent with its intended use in thermally demanding applications such as electronic ballasts and switching regulators. This limit must not be exceeded during operation, and thermal design must account for R_{th j-hs} = 1.15 K/W max and ambient/heatsink conditions to ensure reliable long-term performance of the BUT12AI,127.

Is BUT12AI,127 pin-compatible with other TO220AB npn transistors like BUX87,127?

Yes, BUT12AI,127 uses the standard TO220AB pin configuration (pin 1 = base, pin 2 = collector, pin 3 = emitter, tab = collector), matching BUX87,127 and other devices in that envelope. However, electrical characteristics-including V_CEO, switching speed, and gain-are not interchangeable; substitution requires validation of circuit-level timing, voltage stress, and thermal behavior for the specific BUT12AI,127 application.

What is the typical h_FE range for BUT12AI,127 at I_C = 5 A?

At I_C = 5.0 A and V_CE = 1.5 V, the BUT12AI,127 exhibits h_FEsat = 5.8–12.5, reflecting its saturated gain under hard-drive conditions. This value is lower than small-signal h_FE (14–35 at I_C = 1.0 A), confirming the need for sufficient base drive (≥0.86 A) to maintain low V_CEsat in high-current switching applications using the BUT12AI,127.

Can BUT12AI,127 be used in avalanche mode?

No, the BUT12AI,127 is not rated or characterized for controlled avalanche operation. Its limiting values specify V_CESM = 1000 V as a non-repetitive peak voltage, not an avalanche energy rating. Safe operation requires external clamping or snubbing circuits to avoid exceeding V_CEO = 450 V or V_CESM limits-designs relying on avalanche behavior should select explicitly rated devices instead of the BUT12AI,127.

What thermal interface material is required to achieve the specified R_{th j-hs} of 1.15 K/W for BUT12AI,127?

To achieve the maximum R_{th j-hs} of 1.15 K/W, the BUT12AI,127 datasheet specifies use of heatsink compound and a mounting force of 30 ± 5 newtons applied to the center of the TO220AB envelope. Standard silicone-based thermal pastes or phase-change pads meeting industrial conductivity specs (≥1.0 W/m·K) are appropriate; dry mounting or insufficient pressure will degrade thermal performance and risk exceeding the 150 °C T_j limit of the BUT12AI,127.