onsemi KSH50TF

Overview

KSH50TF from ON Semiconductor (formerly Fairchild) is a high-voltage NPN epitaxial silicon power transistor in TO-252 (DPAK) package, rated for 400 V_CEO, 500 V_CBO, 1 A DC collector current, and 15 W case power dissipation at T_C = 25°C. It serves as a robust switching element in offline AC-DC power supplies, lamp ballasts, and motor control circuits where high breakdown voltage and surface-mount reliability are required.

For engineers reviewing the KSH50TF datasheet, pinout, applications, or equivalent options, this page delivers verified electrical parameters, thermal limits, package geometry, and real-world substitution guidance - all confirmed against the official Fairchild/ON Semiconductor KSH47/KSH50 Rev. 1.1.0 datasheet and TO-252 mechanical drawings.

Technical Context

The KSH50TF operates as a single NPN bipolar junction transistor with epitaxial base construction, optimized for high-voltage switching rather than linear amplification. Its safe operating area (SOA) is defined up to 100 μs pulse width at 200 V_CC, and it exhibits a typical current gain (h_FE) of 30–150 at V_CE = 10 V and I_C = 0.3 A.

Thermal performance is governed by its DPAK package: 15 W maximum collector dissipation at T_C = 25°C drops to zero at T_C = 175°C, with a thermal resistance R_θJC of 1.67°C/W implied by PC = 15 W and ΔT = 25°C. It supports pulse currents up to 2 A with duty cycle ≤2% and pulse width ≤300 μs.

Key Specifications

Pinout & Package

Package: TO-252-3L (DPAK), surface-mount, lead-formed for PCB mounting. Thermal pad on backside provides primary heat path to PCB copper.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BU508AF and MJD127G, the KSH50TF uniquely balances 400 V_CEO rating, 15 W power handling, and moderate h_FE for cost-sensitive, thermally constrained mains-switching designs - making it optimal where both voltage safety margin and manufacturable base drive are required.

Availability

KSH50TF is available at Aetrix Electronics and suitable for AC-DC power supply design, lamp ballast development, and industrial relay driver implementation requiring stable component supply and long-term production continuity.

Supply support for KSH50TF 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 supplier of high-performance silicon solutions for automotive, industrial, cloud computing, and IoT applications, with core expertise in power management and discrete semiconductors.

The KSH50TF belongs to Fairchild's legacy high-voltage bipolar transistor family, designed specifically for cost-effective, surface-mount replacements of through-hole devices like TIP47/TIP50 in offline power conversion and electromagnetic actuator control.

FAQ

What is the maximum continuous collector current rating for KSH50TF?

The KSH50TF has a maximum DC collector current rating of 1 A at T_C = 25°C. This value decreases with rising case temperature per the derating curve in Figure 6 of the datasheet; at T_C = 100°C, the usable I_C drops to approximately 0.5 A. For reliable operation, ensure thermal design maintains T_C ≤ 85°C under full load. The KSH50TF must not be operated beyond its absolute maximum I_C rating even for short durations unless within specified pulse conditions.

Is KSH50TF pin-compatible with the TIP50 transistor?

Yes, the KSH50TF is electrically and mechanically pin-compatible with the TIP50: both use B-C-E pinout order in their respective packages (TO-252 for KSH50TF, TO-220 for TIP50). However, the KSH50TF's DPAK package requires different PCB footprint and thermal layout. While electrical function matches, direct PCB replacement is not possible without board revision - but the KSH50TF serves as a validated surface-mount upgrade path for new designs targeting TIP50 functionality.

What is the safe operating area (SOA) limitation for KSH50TF at 100 μs pulse width?

Per Figure 5 in the KSH47/KSH50 datasheet, the KSH50TF's SOA at 100 μs pulse width supports up to 1.5 A at 400 V_CE and up to 4 A at 100 V_CE. Operation must remain strictly within this boundary to avoid second breakdown. The SOA curve assumes case temperature ≤25°C and no simultaneous voltage/current stress exceeding the plotted envelope. Exceeding these limits - even momentarily - risks irreversible device failure.

Does KSH50TF require a heatsink in typical 1 A switching applications?

Yes, the KSH50TF requires PCB-based thermal management: its 15 W P_C rating assumes direct thermal coupling to ≥1 in² of 2 oz copper with ≥6 thermal vias under the collector pad. Without such layout, power dissipation above ~1.2 W causes rapid T_J rise. In 1 A DC applications, V_CE(sat) ≈ 1 V yields 1 W conduction loss - manageable with proper copper area, but not with minimal traces. Always verify junction temperature using θ_JA estimates or thermal simulation for the actual board stack-up.

What is the emitter-base breakdown voltage specification for KSH50TF?

The KSH50TF has a guaranteed V_EBO (emitter-base breakdown voltage) of 5 V minimum, tested with I_E = 1 mA and I_C = 0. This rating defines the maximum reverse bias allowable across the base-emitter junction during turn-off or negative base drive. Exceeding 5 V in reverse can cause junction avalanche and permanent degradation. In practice, base clamping or resistor-limited drive is recommended to keep V_EB < 4 V during switching transitions.