onsemi KSE340STU

Overview

KSE340STU from ON Semiconductor is an NPN epitaxial silicon power transistor designed for high-voltage general-purpose switching and linear applications, featuring 300 V collector-emitter breakdown voltage (V_CEO), 500 mA continuous collector current (I_C), and 20 W collector dissipation at T_C = 25°C - commonly deployed in flyback transformer drivers and relay interface circuits.

For engineers reviewing the KSE340STU datasheet, pinout, applications, or equivalent options, key selection considerations include its TO-126 package thermal performance, DC current gain range (h_FE = 30–240 at V_CE = 10 V, I_C = 50 mA), safe operating area (SOA) limits, and complementary pairing with KSE350 for push-pull configurations.

Technical Context

The KSE340STU operates as a medium-power bipolar junction transistor optimized for high-voltage switching where robust V_CEO and V_CBO ratings (both 300 V) prevent avalanche failure under transient overvoltage conditions. Its h_FE variation across I_C supports stable biasing in Class-A amplifier stages and saturated-switching designs.

Thermal design relies on case-to-ambient conduction via the TO-126 metal tab; power derating begins at T_C > 25°C per the published 0.167 W/°C slope, and maximum junction temperature is rated at 150°C. The device exhibits low V_BE(sat) and V_CE(sat) in saturation, enabling efficient operation in relay coil drivers and SMPS startup circuits.

Key Specifications

Pinout & Package

Package: TO-126 - thermally enhanced plastic power package with metal tab for mechanical mounting and heat transfer; pin 1 = Emitter, pin 2 = Collector (tab-connected), pin 3 = Base.

Key Features

Applications

Equivalent & Alternatives

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

Compared with KSE340STU, MJE340G offers identical electrical behavior under all operating conditions and is the direct branded successor, whereas KSC2383YTA trades voltage headroom for higher gain and cannot replace KSE340STU in 220 VAC-derived systems.

Availability

KSE340STU is available at Aetrix Electronics and suitable for switch-mode power supply startup, relay driver circuits, flyback transformer drivers, and linear voltage regulator pass element applications requiring stable component supply and long-term industrial availability.

Supply support for KSE340STU 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 is a global semiconductor manufacturer specializing in energy-efficient power management, analog, sensors, and connectivity solutions for automotive, industrial, cloud, and consumer markets.

The KSE340STU belongs to ON Semiconductor's legacy high-voltage bipolar transistor product line, originally developed by Fairchild for robustness in mains-connected power conversion and industrial control interfaces.

FAQ

What is the maximum collector-emitter voltage rating for KSE340STU?

The KSE340STU has a guaranteed minimum collector-emitter breakdown voltage (V_CEO) of 300 V at I_C = 1 mA and I_B = 0. This rating is verified per JEDEC test conditions and defines the absolute maximum DC or peak repetitive voltage the device can block in common-emitter configuration without avalanche conduction. Engineers must maintain design margins below this value in KSE340STU applications involving line transients or inductive kickback.

Is KSE340STU pin-compatible with KSE350?

No, KSE340STU is not pin-compatible with KSE350. While KSE340STU is an NPN transistor and KSE350 is its PNP complement, their pinouts differ: KSE340STU uses Emitter–Collector–Base (1–2–3), whereas KSE350 uses Emitter–Base–Collector (1–2–3). Direct substitution without PCB revision will result in incorrect biasing and potential device failure. Always verify pin assignments using the official ON Semiconductor datasheets for both KSE340STU and KSE350.

What is the thermal resistance from junction to case (R_θJC) for KSE340STU?

The KSE340STU does not specify R_θJC explicitly in its datasheet; however, its power derating curve indicates a thermal resistance of approximately 1.25°C/W (calculated from 20 W at 25°C to 0 W at 175°C). This effective R_θJC assumes full metal-tab contact to a heatsink. Actual thermal performance of KSE340STU depends on mounting pressure, thermal interface material, and heatsink fin density - measured values may vary ±15% in production assemblies.

Can KSE340STU be used in linear amplifier applications?

Yes, KSE340STU is suitable for Class-A and Class-AB linear amplifier stages where moderate voltage swing (≤200 V) and current drive (≤300 mA) are required. Its h_FE consistency across I_C, low V_BE(sat), and SOA compliance up to 10 µs pulses support stable quiescent biasing. However, due to its 20 W P_C limit and thermal mass, KSE340STU is best applied in low-to-medium fidelity audio preamps or sensor signal conditioning - not high-power output stages. Thermal design remains critical in KSE340STU linear use.

Does KSE340STU have lead-free and RoHS-compliant packaging?

Yes, KSE340STU is manufactured in lead-free, RoHS-compliant packaging per ON Semiconductor's post-2006 environmental policy. The TO-126 package uses matte tin plating on leads and complies with JEDEC J-STD-020 moisture sensitivity level (MSL) 1. Full compliance documentation, including substance declarations and test reports for KSE340STU, is available through ON Semiconductor's Quality & Environmental portal and authorized distributors' material databases.