onsemi KSH340TF

Overview

KSH340TF from ON Semiconductor is a high-voltage NPN epitaxial silicon power transistor in D-PAK surface-mount package, rated for 300 V V_CEO, 0.5 A DC collector current, and 15 W collector dissipation at T_C = 25°C; it delivers h_FE of 30–240 at V_CE = 10 V and I_C = 50 mA, and is used in flyback converter switching stages requiring robust voltage blocking and pulse-current capability.

For engineers reviewing the KSH340TF datasheet, pinout, applications, or equivalent options, key selection criteria include its 300 V sustaining voltage (V_CEO(sus)), low saturation voltage under pulse conditions, thermal derating behavior above 25°C case temperature, and compatibility with automated SMT assembly due to its standardized D-PAK footprint.

Technical Context

The KSH340TF operates as a single-element NPN bipolar junction transistor optimized for high-voltage switching in offline power supplies. Its design emphasizes high breakdown voltage (V_CBO = 300 V, V_CEO = 300 V) and controlled gain (h_FE = 30–240) across defined bias conditions, supporting stable operation in discontinuous conduction mode (DCM) flyback topologies.

It features a thermally efficient D-PAK package with direct die-to-case thermal path, enabling 15 W dissipation at T_C = 25°C but requiring linear derating to zero at 150°C junction temperature. Pulse operation is validated per PW ≤ 300 µs and duty cycle ≤ 2%, with I_CP = 0.75 A specified under those conditions.

Key Specifications

Pinout & Package

Package: D-PAK (TO-252), surface-mount, lead-formed for automated placement; thermal pad on underside requires soldered connection to PCB ground plane for optimal heat transfer.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MJD340G and BU508AF, the KSH340TF offers the best balance of voltage rating, gain consistency, and D-PAK manufacturability for cost-sensitive 10–20 W flyback designs-neither alternative matches its combination of 300 V, guaranteed h_FE ≥ 30, and SMT-ready form factor.

Availability

KSH340TF is available at Aetrix Electronics and suitable for offline AC/DC adapters, industrial sensor power supplies, and isolated bias rails requiring stable component supply with consistent parametric screening and traceable lot history.

Supply support for KSH340TF 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 supplier delivering energy-efficient, intelligent power and sensing solutions for automotive, industrial, cloud, medical, and edge applications.

The KSH340TF belongs to ON Semiconductor's high-voltage bipolar transistor product line, designed specifically for cost-optimized, high-reliability switching in offline power conversion systems where voltage robustness and thermal stability are critical.

FAQ

What is the maximum continuous collector current for the KSH340TF?

The KSH340TF has a maximum DC collector current (I_C) of 0.5 A at T_C = 25°C. This rating decreases with rising case temperature and must be derated linearly to zero at 150°C junction temperature. For sustained operation above 25°C, PCB copper area and airflow must be evaluated to maintain safe thermal margins. The KSH340TF datasheet specifies this limit under defined test conditions and should be validated in the final application environment.

Does the KSH340TF have a documented pulse current rating?

Yes, the KSH340TF is rated for a peak collector current (I_CP) of 0.75 A under pulsed conditions: pulse width ≤ 300 µs and duty cycle ≤ 2%. This rating supports transient overload handling during startup or fault recovery in flyback converters. The KSH340TF safe operating area (SOA) curve in the datasheet confirms this capability, and designers must ensure gate/base drive timing remains within these constraints to avoid secondary breakdown.

Is the KSH340TF pin-compatible with other D-PAK NPN transistors like MJD340G?

Yes, the KSH340TF and MJD340G share identical D-PAK (TO-252) package dimensions and pinout: Pin 1 = Base, Pin 2 = Collector, Pin 3 = Emitter. However, they are not drop-in replacements due to differences in minimum h_FE (30 vs. 20) and saturation characteristics. The KSH340TF may require revised base resistor values in existing MJD340G designs to ensure full saturation under worst-case conditions.

What is the junction-to-case thermal resistance (R_θJC) of the KSH340TF?

The KSH340TF datasheet does not publish R_θJC as a discrete value. Instead, thermal performance is characterized by its 15 W collector dissipation at T_C = 25°C and linear derating above that temperature. Engineers should use the published power derating curve (Figure 4) and apply measured case temperature to determine allowable power. For accurate thermal modeling, ON Semiconductor recommends using the KSH340TF's package outline and thermal pad layout guidelines in conjunction with standard D-PAK thermal simulation models.

Can the KSH340TF be used in linear amplifier applications?

No, the KSH340TF is not intended for linear amplification. It is optimized for switching operation with emphasis on high-voltage blocking, fast turn-off, and pulse-current capability. Its h_FE variation across current and temperature, lack of specified linearity parameters (e.g., distortion, f_T), and SOA limitations make it unsuitable for analog signal amplification. The KSH340TF is specified and tested exclusively for switching applications such as flyback and forward converters.