onsemi FJPF2145TU

Overview

FJPF2145TU from ON Semiconductor (formerly Fairchild) is an ESBC™-rated NPN power transistor designed for high-voltage, high-speed switching in cascode configurations with a low-voltage MOSFET. It delivers 800 V V_CEO, 5 A I_C, 0.085 V V_CE(sat) at 1 A, avalanche-rated operation, and wide RBSOA up to 1100 V - enabling robust use in smart breakers and industrial SMPS.

For engineers reviewing the FJPF2145TU datasheet, pinout, applications, or equivalent options, key selection criteria include its TO-220F package, absence of Miller capacitance in ESBC™ mode, 15 MHz f_T, and verified 15 mJ avalanche energy rating under standardized lab conditions.

Technical Context

The FJPF2145TU operates as the bipolar half of an Emitter-Switched Bipolar/MOSFET Cascode (ESBC™), where it handles high-voltage blocking while the companion MOSFET (e.g., FDC655) provides low-loss, fast gate control. Its dedicated high-voltage bipolar process enables square RBSOA and eliminates parasitic transistors, preventing static dv/dt-induced false triggering.

When configured in ESBC™, the device achieves sub-100 ns inductive current fall time (t_f = 50 ns at I_C = 1 A), 0.209 V V_CS(ON) at 2 A, and no Miller capacitance - reducing driving power requirements and enabling direct interface with off-the-shelf PWM controllers without complex gate drive circuitry.

Key Specifications

Pinout & Package

Package: TO-220F (full-pack, insulated tab, 3-lead molded). Pin 1 = Base, Pin 2 = Collector, Pin 3 = Emitter - confirmed via Figure 1 and internal schematic in datasheet Rev. 1.0.0.

Key Features

Applications

Equivalent & Alternatives

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

Compared with STN12100K and MJD127G, the FJPF2145TU uniquely combines 800 V blocking, 5 A current, avalanche rating, and ESBC™-specific optimization - making it the only choice among the three for high-reliability, high-voltage cascode switching in smart meters and industrial SMPS.

Availability

FJPF2145TU is available at Aetrix Electronics and suitable for smart grid protection, industrial SMPS, motor drive inverters, and ignition systems requiring stable component supply across multi-year production cycles.

Supply support for FJPF2145TU 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

ON Semiconductor (formerly Fairchild Semiconductor) is a global supplier of energy-efficient semiconductor solutions, specializing in power management, analog, sensors, and logic devices for industrial, automotive, and computing markets.

The FJPF2145TU belongs to Fairchild's ESBC™-optimized power transistor family, engineered specifically to replace IGBTs and high-voltage MOSFETs in cascode topologies where high dv/dt immunity, low switching loss, and avalanche ruggedness are critical.

FAQ

What is the maximum operating junction temperature for the FJPF2145TU?

The FJPF2145TU has a specified operating junction temperature range of –55°C to +125°C. This allows reliable deployment in harsh environments such as industrial motor drives and outdoor smart meter enclosures. Derating curves in Figure 20 confirm usable power dissipation down to 0 W at T_C = 150°C, ensuring design margin under thermal stress. The FJPF2145TU must be mounted with appropriate thermal interface material to maintain T_J ≤ 125°C under full load.

Is the FJPF2145TU pin-compatible with other TO-220F NPN transistors?

The FJPF2145TU uses standard TO-220F pinout (Pin 1 = Base, Pin 2 = Collector, Pin 3 = Emitter), matching mechanical and electrical layout conventions for TO-220F-packaged NPN transistors. However, electrical characteristics-including V_CEO, h_FE, and R_θJC-are unique to the FJPF2145TU. Direct substitution requires verification of drive current, thermal design, and avalanche requirements. The FJPF2145TU is not a generic drop-in replacement despite identical pin assignment.

Does the FJPF2145TU require a heatsink in typical applications?

Yes - the FJPF2145TU dissipates up to 40 W at T_C = 25°C, and its R_θJC of 3.125 °C/W necessitates a heatsink for any sustained I_C > 1 A. Without heatsinking, junction temperature rises rapidly beyond safe limits. The TO-220F insulated tab enables direct mounting to grounded heatsinks, and thermal design must account for ambient temperature, airflow, and duty cycle. For 30 W SMPS use, a 10–15°C/W heatsink is recommended. The FJPF2145TU's thermal performance is validated only with proper mechanical mounting per datasheet Figure 34.

Can the FJPF2145TU be used outside of ESBC™ configurations?

Yes - the FJPF2145TU functions as a standalone high-voltage NPN power transistor in conventional common-emitter or common-base topologies. Its 800 V V_CEO, 5 A I_C, and 15 mJ avalanche rating support use in linear regulators, lamp dimmers, and relay drivers. However, its ESBC™-specific optimizations - including minimized Miller effect and tailored h_FE profile - deliver maximum benefit only when paired with a compatible low-voltage MOSFET like the FDC655. The FJPF2145TU remains fully functional and rated in non-cascode applications.

What is the base-emitter leakage current specification for the FJPF2145TU?

The FJPF2145TU specifies I_EBO (emitter-base leakage) as ≤10 μA at V_EB = 5 V and I_C = 0, per Electrical Characteristics table on page 2 of the datasheet. This low leakage supports stable biasing in high-impedance drive circuits and ensures minimal standby current in always-on protection systems. No separate I_CBO or I_CEO leakage is specified beyond the 10 μA I_EBO limit. Designers should verify actual leakage under operating conditions, as the FJPF2145TU's leakage may increase near maximum T_J.