onsemi MJE703STU

Overview

MJE703STU from ON Semiconductor (formerly Fairchild) is a PNP epitaxial silicon Darlington transistor in TO-126 package, rated for -80 V V_CEO, -4 A I_C, and 40 W P_C at T_C=25°C. It features built-in base-emitter resistors (R1 ≈ 10 kΩ, R2 ≈ 0.6 kΩ), h_FE ≥ 750 at I_C = -2 A, and V_CE(sat) ≤ -2.8 V at I_C = -2 A / I_B = -40 mA. Used in high-gain linear and switching applications such as relay drivers and power supply error amplifiers.

For engineers reviewing the MJE703STU datasheet, pinout, applications, or equivalent options, key selection criteria include its -80 V collector-emitter breakdown voltage, integrated bias resistors enabling single-resistor base drive, Darlington topology for high current gain with low base drive, and TO-126 thermal performance supporting 40 W dissipation at case temperature ≤25°C.

Technical Context

The MJE703STU implements a monolithic PNP Darlington pair with on-chip base-emitter resistors (R1 ≈ 10 kΩ, R2 ≈ 0.6 kΩ), eliminating external bias components. Its structure delivers h_FE ≥ 750 at I_C = -2 A and V_CE = -3 V, while maintaining V_CE(sat) ≤ -2.8 V under same conditions.

Designed for medium-power linear and switching roles, it operates with V_EB(on) ≤ -2.5 V at I_C = -2 A and supports safe operating area up to -80 V / -4 A with derating above 25°C case temperature. Junction temperature is rated to 150°C, and storage range spans -55°C to +150°C.

Key Specifications

Pinout & Package

Package: TO-126 - Three-lead plastic power package with metal tab for heatsink mounting; lead spacing matches industry-standard TO-126 footprint (16.10 mm × 13.06 mm × 14.20 mm max height).

Key Features

Applications

Equivalent & Alternatives

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

Compared with BDX54C and MJE702STU, the MJE703STU offers optimized gain at -2 A (h_FE ≥ 750), consistent -80 V rating, and TO-126 compatibility-making it ideal for space-constrained, medium-power PNP Darlington applications requiring predictable gain and thermal performance.

Availability

MJE703STU is available at Aetrix Electronics and suitable for industrial motor control, telecom power management, relay interface modules, and LED current regulation requiring stable component supply and long-term obsolescence support.

Supply support for MJE703STU 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 semiconductor supplier focused on energy-efficient electronics, with leadership in power management, analog, and discrete devices.

The MJE703STU belongs to Fairchild's legacy bipolar power transistor family, designed specifically for high-gain, medium-power linear and switching applications in industrial and telecom infrastructure where reliability and thermal stability are critical.

FAQ

What is the maximum collector-emitter voltage rating for MJE703STU?

The MJE703STU has a guaranteed minimum collector-emitter breakdown voltage (V_CEO) of -80 V at I_C = -10 mA and I_B = 0. This rating applies across the full operating temperature range and defines the absolute maximum voltage that can be applied between collector and emitter with base open before device breakdown occurs. The MJE703STU must not be operated beyond this limit in any circuit configuration.

Does MJE703STU require an external base resistor for operation?

No, the MJE703STU does not require an external base resistor because it integrates two on-die resistors: R1 ≈ 10 kΩ between base and emitter, and R2 ≈ 0.6 kΩ between base and collector. These resistors provide self-biasing and ensure turn-off when drive is removed, making the MJE703STU compatible with direct TTL or CMOS logic-level inputs without additional components.

What is the DC current gain (hFE) specification for MJE703STU at full rated current?

The MJE703STU guarantees h_FE ≥ 750 at V_CE = -3 V and I_C = -2 A. At the absolute maximum continuous collector current of -4 A, h_FE drops to ≥100 (per datasheet). Designers should reference the -2 A condition for high-gain operation and confirm gain margin in linear applications where collector current approaches -4 A.

Can MJE703STU be used as a direct replacement for MJE701STU?

No, MJE703STU is not a direct replacement for MJE701STU. While both are PNP Darlington transistors in TO-126, the MJE701STU is rated for -60 V V_CEO and specifies h_FE ≥ 750 only at I_C = -1.5 A. Substituting MJE703STU may introduce overvoltage stress in circuits designed for -60 V operation, and its higher voltage rating does not guarantee functional equivalence without circuit revalidation.

What thermal derating applies to MJE703STU above 25°C case temperature?

The MJE703STU's collector power dissipation must be linearly derated above 25°C case temperature at 0.32 W/°C, reaching zero at 150°C. For example, at T_C = 75°C, maximum allowable P_C = 40 W − (75 − 25) × 0.32 W = 24 W. This derating curve is defined in Figure 6 of the original Fairchild datasheet and must be applied in heatsink design and thermal modeling for the MJE703STU.