onsemi KSE703S

Overview

KSE703S from Fairchild Semiconductor 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, with built-in base-emitter resistors (R1 ≈ 10 kΩ, R2 ≈ 0.6 kΩ), used in high-current linear amplification and relay/inductive load switching.

For engineers reviewing the KSE703S datasheet, pinout, applications, or equivalent options, key selection criteria include its -80 V collector-emitter breakdown voltage, Darlington h_FE ≥ 750 at I_C = -2 A, V_CE(sat) ≤ -2.8 V, integrated bias network, and TO-126 thermal performance for industrial power control designs.

Technical Context

The KSE703S implements a monolithic Darlington pair with on-chip base-emitter resistors enabling self-biasing and simplified drive circuitry. It delivers high DC current gain (h_FE ≥ 750) at moderate collector currents (-1.5 A to -2 A) while maintaining robust safe operating area up to 40 W at 25°C case temperature.

Its complementary structure-paired with KSE803-supports push-pull output stages. The device operates with V_BE(on) ≈ -2.5 V at I_C = -2 A and exhibits V_CE(sat) ≤ -2.8 V under matched base drive (I_B = -40 mA), confirming suitability for saturated-switching applications requiring low conduction loss.

Key Specifications

Pinout & Package

Package: TO-126 (3-lead, plastic, through-hole), with tab connected to collector for direct heatsink mounting and thermal management.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MJD703 and KSE702, the KSE703S provides superior integration (on-chip R1/R2), higher voltage rating (-80 V), and guaranteed high h_FE at -2 A-making it optimal for compact, reliable, medium-voltage industrial switching where board space and thermal management are constrained.

Availability

KSE703S is available at Aetrix Electronics and suitable for industrial relay drivers, DC motor controllers, and linear power supply pass devices requiring stable component supply, long-lifecycle support, and traceable sourcing.

Supply support for KSE703S 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 KSE703S belongs to Fairchild's legacy high-power PNP Darlington family, designed specifically for industrial control, power conversion, and electromechanical actuation where ruggedness, integrated biasing, and thermal reliability are critical.

FAQ

What is the maximum collector-emitter voltage rating for the KSE703S?

The KSE703S has a maximum collector-emitter voltage rating (V_CEO) of -80 V at T_C = 25°C. This rating is confirmed in the Absolute Maximum Ratings table and verified in the Electrical Characteristics section under BV_CEO test conditions (I_C = -10 mA, I_B = 0). Operation beyond this voltage risks avalanche breakdown and permanent device failure. Derating is required above 25°C case temperature per the power derating curve in the datasheet.

Does the KSE703S have built-in base resistors, and what are their values?

Yes, the KSE703S features monolithic construction with two built-in base-emitter resistors: R1 ≈ 10 kΩ and R2 ≈ 0.6 kΩ, as shown in the Equivalent Circuit diagram. These resistors stabilize biasing, reduce external component count, and improve turn-off speed compared to standard Darlingtons. Their values are specified in the datasheet schematic and confirmed in application notes for the KSE700–703 series.

What is the DC current gain (hFE) specification for the KSE703S, and at what conditions is it guaranteed?

The KSE703S guarantees h_FE ≥ 750 at V_CE = -3 V and I_C = -2 A, per the Electrical Characteristics table. This minimum gain applies specifically to the KSE701/KSE703 variants and is measured under controlled DC conditions. Gain drops to ≥100 at I_C = -4 A, reflecting typical Darlington behavior at peak current.

What package type does the KSE703S use, and how is the collector connected internally?

The KSE703S uses the TO-126 package, a 3-lead through-hole plastic package with a metal tab. As shown in the Package Dimensions and Pin Configuration diagrams, the collector (Pin 2) is electrically and thermally connected to the metal tab, enabling direct attachment to a heatsink for thermal management. This mechanical-electrical integration is critical for sustaining its 40 W power dissipation rating.

Is the KSE703S pin-compatible with other devices in the KSE700 series, such as the KSE700 or KSE702?

Yes, all KSE700-series devices-including KSE700, KSE701, KSE702, and KSE703-share identical TO-126 pinout (Emitter–Collector–Base) and mechanical dimensions. However, electrical ratings differ: KSE700/KSE701 are rated for -60 V V_CEO, while KSE702/KSE703 are rated for -80 V. Substituting KSE703S for KSE700 requires verifying system voltage margins but introduces no PCB layout changes.