onsemi MJE803

Overview

MJE803 from onsemi is an NPN silicon Darlington power transistor in TO-225 package, rated for 80 V_CEO, 4.0 A collector current, and 40 W power dissipation at T_C = 25°C, with typical DC current gain (h_FE) of 750 at I_C = 2.0 A and V_CE = 3.0 V - used in low-speed switching and linear amplifier stages of industrial control power supplies.

For engineers reviewing the MJE803 datasheet, pinout, applications, or equivalent options, key selection criteria include V_CEO = 80 V, I_C = 4.0 A, h_FE ≥ 750 (min), V_CE(sat) ≤ 2.8 V at I_C/I_B = 250, and thermal resistance R_JC = 3.12 °C/W - all critical for thermal-limited linear regulator and relay driver designs.

Technical Context

The MJE803 is a monolithic NPN Darlington pair with built-in base-emitter resistors to suppress leakage multiplication, enabling stable high-gain operation without external bias stabilization. It operates in linear and saturation regions with guaranteed h_FE ≥ 750 at I_C = 2.0 A and V_CE = 3.0 V, and exhibits V_CE(sat) ≤ 2.8 V under same conditions.

Its safe operating area (SOA) is thermally limited up to 150°C junction temperature, with second-breakdown constraints active above 1 ms pulse width; derating begins at 25°C case temperature at 0.32 W/°C, supported by R_JA = 83.3 °C/W and R_JC = 3.12 °C/W.

Key Specifications

Pinout & Package

Package: TO-225 (Case 77-09, Style 1), plastic through-hole package with metal tab connected to collector (pins 2 and 4). Mounting tab is electrically common to collector terminals and serves as primary heat path.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TIP122 and BD679, the MJE803 offers superior thermal performance (R_JC = 3.12 °C/W) and built-in leakage suppression in a TO-225 footprint, making it optimal for space-constrained, thermally demanding industrial relay and linear supply designs where reliability at elevated temperature is critical.

Availability

MJE803 is available at Aetrix Electronics and suitable for industrial relay drivers, linear power supply pass elements, and DC load switches requiring stable component supply across extended production lifecycles.

Supply support for MJE803 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

onsemi (formerly ON Semiconductor) is a global semiconductor supplier specializing in energy-efficient power, analog, sensor, and connectivity solutions for automotive, industrial, and cloud infrastructure markets.

The MJE803 belongs to onsemi's legacy plastic Darlington power transistor family designed specifically for robust, low-speed switching and linear amplification in harsh industrial environments - emphasizing thermal stability, leakage immunity, and long-term reliability.

FAQ

What is the maximum collector-emitter voltage rating for the MJE803?

The MJE803 has a maximum collector-emitter voltage (V_CEO) rating of 80 Vdc, verified per the onsemi datasheet Rev. 12. This rating applies under standard test conditions (I_C = 50 mA, I_B = 0) and defines the absolute upper limit for safe operation in DC or pulsed applications. Exceeding 80 V risks avalanche breakdown and permanent device failure. The MJE803 is therefore suited for 24 V and 48 V industrial systems but not for 100 V bus architectures.

Does the MJE803 include built-in base-emitter resistors?

Yes, the MJE803 features monolithic construction with integrated base-emitter resistors to suppress leakage current multiplication - a key differentiator from basic bipolar transistors. This design improves thermal stability at elevated junction temperatures (up to +150°C), reduces risk of thermal runaway in linear applications, and eliminates the need for external leakage-compensation networks in relay driver or power supply circuits using the MJE803.

What is the thermal resistance from junction to case (R_JC) for the MJE803?

The MJE803 has a maximum junction-to-case thermal resistance (R_JC) of 3.12 °C/W, measured under specified test conditions per the onsemi datasheet. This value reflects the intrinsic thermal path from silicon die to the metal tab (collector), and directly determines heatsink sizing: for example, maintaining T_J ≤ 125°C at 20 W dissipation requires a heatsink with θ_SA ≤ 19.4 °C/W when ambient is 50°C. The MJE803's low R_JC supports compact thermal design versus alternatives like the TIP122 (R_JC = 4.0 °C/W).

Can the MJE803 be used in linear regulator applications?

Yes, the MJE803 is explicitly qualified for linear amplifier and regulator use, with SOA curves validated up to DC operation at T_J = 150°C. Its guaranteed h_FE ≥ 750 at I_C = 2.0 A and V_CE = 3.0 V ensures predictable base current demand, while V_CE(sat) ≤ 2.8 V minimizes dropout-related losses. When used as a series pass transistor in a 3 A, 24 V output supply, the MJE803 delivers stable regulation with proper heatsinking and foldback current limiting.

What package type does the MJE803 use, and how are its pins configured?

The MJE803 uses the TO-225 package (Case 77-09, Style 1), a three-lead through-hole plastic package with collector terminals on pins 2 and 4 and the metal tab. Pin 1 is emitter, pin 3 is base. The collector-tab connection requires electrical isolation from the PCB ground plane unless the collector node is at system ground potential. This configuration is standardized across the MJE800G series and ensures compatibility with existing TO-225 footprints and heatsink clamps.