onsemi KSE802STU

Overview

KSE802STU from onsemi is an NPN epitaxial silicon Darlington transistor in TO-126-3LD package, featuring monolithic construction with built-in base-emitter resistors, h_FE ≥ 750 at I_C = 1.5 A, V_CEO = 60 V, and P_C = 40 W at T_C = 25°C - used in high-current linear amplification and relay/inductive load switching.

For engineers reviewing the KSE802STU datasheet, pinout, applications, or equivalent options, key selection criteria include guaranteed DC current gain at 1.5–4 A collector current, saturation voltage under defined I_B/I_C conditions, thermal derating behavior, and compatibility with complementary KSE702 devices in push-pull output stages.

Technical Context

This Darlington pair integrates two NPN transistors and two on-chip resistors (R1 ≈ 10 kΩ, R2 ≈ 0.6 kΩ) to enable self-biasing and reduce external component count. It operates as a single high-gain switching or amplifying element with V_BE(on) = 2.5–3 V and V_CE(sat) = 2.5–3 V across its rated I_C range.

The device is optimized for medium-power linear and switching applications where low base drive current and stable h_FE > 750 are required. Its TO-126-3LD package supports direct heatsink mounting and provides thermal resistance θ_JC suitable for continuous 40 W dissipation at case temperature ≤ 25°C.

Key Specifications

Pinout & Package

Package: TO-126-3LD (Case 340AS), surface-mountable through-hole package with integral metal tab for mechanical mounting and thermal conduction to heatsink.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MJD122G and BD679A, the KSE802STU offers optimal balance of voltage rating, gain stability at 1.5–4 A, and TO-126-3LD mechanical compatibility - making it preferred for space-constrained industrial controls where pinout retention and thermal interface consistency are critical.

Availability

KSE802STU is available at Aetrix Electronics and suitable for industrial relay drivers, DC motor speed control, and linear power supply pass applications requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for KSE802STU 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 focused on energy-efficient electronics, with leadership in power management, analog, sensors, and discrete devices.

The KSE802STU belongs to onsemi's high-reliability discrete transistor product line, engineered specifically for industrial automation, power conversion, and ruggedized control systems demanding consistent parametric performance across temperature and lifetime.

FAQ

What is the pin configuration of the KSE802STU?

The KSE802STU uses a TO-126-3LD package with pin 1 as Emitter, pin 2 as Collector, and pin 3 as Base - matching the standard E-C-B order shown in the official onsemi mechanical drawing Case 340AS. This configuration is confirmed in the device marking diagram and equivalent circuit schematic in the KSE800/D datasheet, which applies identically to KSE802STU per onsemi ordering documentation.

Is the KSE802STU RoHS compliant?

Yes, the KSE802STU is explicitly marked as Pb-Free in the onsemi datasheet and shipping information, meeting RoHS Directive 2011/65/EU requirements. The "STU" suffix denotes the Pb-free version in TO-126-3LD packaging, with full compliance verified by onsemi's material declarations and test reports.

What is the minimum hFE guaranteed for KSE802STU at 4 A collector current?

The KSE802STU guarantees h_FE ≥ 100 at I_C = 4 A, V_CE = 3 V, per the Electrical Characteristics table in the KSE800/D datasheet. This lower bound ensures usable current gain even at maximum rated current, supporting reliable base drive sizing in high-load switching applications.

Can KSE802STU replace KSE800STU in existing designs?

Yes, the KSE802STU is a direct functional replacement for KSE800STU with identical electrical specifications, pinout, package, and thermal characteristics. Both share the same datasheet (KSE800/D), and the "802" designation reflects minor process or screening enhancements without parameter or mechanical changes.

What is the safe operating area (SOA) limitation for KSE802STU at 100°C case temperature?

At T_C = 100°C, the KSE802STU's maximum continuous collector current is reduced to approximately 2.7 A per the Power Derating curve (Figure 6), and pulsed operation must stay within the SOA boundary defined in Figure 5 - limiting V_CE × I_C product to avoid secondary breakdown during transient overload conditions.