onsemi FJP5021RTU

Overview

FJP5021RTU from Fairchild Semiconductor is an NPN silicon power transistor designed for high-voltage switching applications, featuring 800 V collector-base breakdown voltage (BVCBO), 500 V collector-emitter sustaining voltage (VCEX(sus)), and 5 A DC collector current (IC), commonly used in flyback converters and snubberless AC-DC power supplies.

For engineers reviewing the FJP5021RTU datasheet, pinout, applications, or equivalent options, key selection criteria include its 500 V BVCEO rating, 1 µs typical fall time (tF), TO-220 package thermal performance, and verified safe operating area (SOA) under inductive switching conditions.

Technical Context

The FJP5021RTU employs a planar epitaxial base structure optimized for rugged high-voltage operation, with specified reverse-bias SOA up to 1000 V at 10 µs pulse width and clamped inductive turn-off capability at IC = 2.5 A, IB1 = −IB2 = 1 A. Its 18 MHz fT and low Cob (80 pF) support fast switching in hard-switched topologies.

It operates with fixed three-terminal configuration (Base–Collector–Emitter), requires external base drive for saturation control, and exhibits defined VCE(sat) = 1 V and VBE(sat) = 1.5 V at IC = 3 A / IB = 0.6 A - enabling predictable conduction loss calculation in primary-side switch designs.

Key Specifications

Pinout & Package

Package: TO-220 (3-lead, straight lead, insulated tab). Dimensions conform to JEDEC TO-220AB standard with 15.90 mm body length, 10.08 mm width, and 4.50 mm lead thickness.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar high-voltage NPN switching transistor applications.

Compared with FJP5021RTU, MJD127G trades voltage capability for gain and package form factor, while BU508AF extends voltage margin at the cost of switching speed - making FJP5021RTU the optimal balance for 500 V-class flyback and inductive switching where both ruggedness and speed matter.

Availability

FJP5021RTU is available at Aetrix Electronics and suitable for offline AC-DC power supplies, industrial relay drivers, and ignition circuit designs requiring stable component supply across multi-year production cycles.

Supply support for FJP5021RTU 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

Fairchild Semiconductor was a U.S.-based semiconductor company specializing in power management, analog, and discrete components before its acquisition by ON Semiconductor in 2016.

The FJP5021RTU belongs to Fairchild's high-voltage bipolar transistor product line, engineered specifically for reliable switching in cost-sensitive, high-reliability power conversion systems operating up to 500 V.

FAQ

What is the maximum junction temperature rating for the FJP5021RTU?

The FJP5021RTU has a maximum junction temperature (TJ) rating of 150 °C, as specified in its Absolute Maximum Ratings table. This allows operation in high-ambient environments when mounted with appropriate heatsinking. Thermal design must ensure that actual TJ under worst-case load and ambient conditions remains below this limit to maintain reliability and avoid degradation of hFE or breakdown characteristics. The FJP5021RTU datasheet provides derating curves for power dissipation versus case temperature.

Does the FJP5021RTU have a built-in base-emitter resistor?

No, the FJP5021RTU does not include any integrated base-emitter resistors. It is a standard three-terminal NPN bipolar junction transistor requiring external base drive circuitry to control turn-on and turn-off behavior. Base current must be actively supplied and sunk - typically via separate driver stages or resistor networks - to achieve the specified VCE(sat) and switching times. This distinguishes it from digital transistors or pre-biased devices.

Is the FJP5021RTU pin-compatible with other TO-220 NPN transistors like the TIP41C?

The FJP5021RTU uses the standard TO-220AB pinout (Base–Collector–Emitter, left-to-right), matching mechanical and electrical pin assignments of TIP41C and similar devices. However, due to its significantly higher voltage ratings (800 V VCBO vs. 100 V for TIP41C), direct substitution is unsafe without verifying circuit stress margins. Voltage, SOA, and switching performance differences require full revalidation if replacing TIP41C with FJP5021RTU.

What is the guaranteed minimum hFE for the FJP5021RTU at IC = 3 A?

At IC = 3 A and VCE = 5 V, the FJP5021RTU has a guaranteed minimum hFE of 8, per the "hFE2" parameter in its Electrical Characteristics table. This value applies to the standard R-class device (hFE1 = 15–30, hFE2 = 8–?); actual units may exceed this depending on hFE binning. Designers should use hFE = 8 for worst-case base drive sizing to ensure saturation under all operating conditions.

Can the FJP5021RTU be used in avalanche mode?

The FJP5021RTU is not rated or characterized for repetitive avalanche operation. While its 800 V VCBO and 500 V VCEO suggest single-pulse avalanche capability, Fairchild's datasheet does not specify avalanche energy (EAS) or ruggedness testing. For circuits relying on controlled avalanche (e.g., some ZVS topologies), a device explicitly rated for avalanche - such as certain PowerTrench MOSFETs - is recommended instead of the FJP5021RTU.