onsemi KST43MTF

Overview

KST43MTF from ON Semiconductor (formerly Fairchild) is a high-voltage NPN epitaxial silicon transistor in SOT-23 package, rated for 200 V collector-base and collector-emitter breakdown voltage, 500 mA continuous collector current, and 350 mW power dissipation - used in high-voltage switching and linear amplification circuits such as CRT deflection drivers and industrial power supply control stages.

For engineers reviewing the KST43MTF datasheet, pinout, applications, or equivalent options, key selection criteria include its 200 V BV_CEO, 50 MHz f_T, 40 minimum h_FE at 10 mA, low 0.5 V V_CE(sat), and SOT-23 footprint compatibility with space-constrained HV bias and switching designs.

Technical Context

The KST43MTF operates as a general-purpose high-voltage NPN bipolar junction transistor with epitaxial base construction enabling stable gain and breakdown performance up to 200 V. Its DC current gain (h_FE) ranges from 25 to 40 across 1–30 mA collector currents, and it delivers 50 MHz current-gain bandwidth under 20 V V_CE and 10 mA I_C.

Thermal resistance of 357 °C/W (R_θJA) and junction temperature range of –55 °C to +150 °C support operation in industrial ambient environments. The device exhibits low output capacitance (4 pF Cob at 20 V), enabling use in moderate-frequency switching applications where capacitive loading must be minimized.

Key Specifications

Pinout & Package

SOT-23 (TO-236AB) 3-lead plastic surface-mount package with standard JEDEC outline (MA03D), 1.30 mm × 2.92 mm footprint, 1.20 mm max height, and gull-wing leads for reflow assembly.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MMBT4401 and KST42MTF, the KST43MTF uniquely balances 200 V ruggedness, 50 MHz bandwidth, and SOT-23 compactness - making it optimal for cost-sensitive industrial HV interfaces where 300 V is excessive but 40 V is insufficient.

Availability

KST43MTF is available at Aetrix Electronics and suitable for industrial power supply control, high-voltage bias generation, CRT deflection driver stages, and relay/solenoid interface applications requiring stable component supply and long-term obsolescence management.

Supply support for KST43MTF 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 IoT applications.

The KST43MTF belongs to Fairchild's legacy high-voltage bipolar transistor family, designed specifically for robust, low-cost switching and linear amplification in industrial and consumer power systems where reliability at elevated voltages is essential.

FAQ

What is the maximum collector-emitter voltage rating for KST43MTF?

The KST43MTF has a maximum collector-emitter breakdown voltage (V_CEO) of 200 V at T_A = 25 °C. This rating applies under open-base conditions with I_C = 1 mA. Operation above this voltage risks irreversible avalanche failure. Derating is required at elevated temperatures per the datasheet's thermal curves. The KST43MTF is intended for use in circuits where peak V_CE remains below 200 V, such as 120 VAC-derived supplies or flyback clamp nodes.

Does KST43MTF have a documented pinout compatible with standard SOT-23 footprints?

Yes, the KST43MTF uses the standard SOT-23 (TO-236AB) package with pin 1 = Base, pin 2 = Emitter, pin 3 = Collector - matching JEDEC MO-178 and Fairchild MA03D mechanical drawing. This pinout is identical to KST42MTF and widely supported by PCB land patterns. No adapter or footprint modification is needed when substituting within the KST42/KST43 family.

What is the typical DC current gain (hFE) of KST43MTF at 10 mA collector current?

The KST43MTF exhibits a minimum h_FE of 40 at V_CE = 10 V and I_C = 10 mA, with typical values ranging from 60 to 100. This gain is specified under pulsed test conditions (≤300 μs, ≤2% duty cycle) to minimize self-heating effects. At 30 mA I_C, h_FE remains ≥40, confirming stable current amplification across its rated operating range.

Can KST43MTF be used in linear amplifier configurations?

Yes, the KST43MTF supports linear operation with verified parameters including V_BE(sat) = 0.9 V, Cob = 4 pF, and f_T = 50 MHz. Its epitaxial base structure provides consistent h_FE vs. I_C behavior, making it suitable for low-distortion audio preamplifiers and instrumentation buffer stages - provided power dissipation stays within 350 mW and thermal design accounts for R_θJA = 357 °C/W.

Is KST43MTF RoHS compliant and halogen-free?

Yes, the KST43MTF is RoHS-compliant and halogen-free per ON Semiconductor's product change notices and packaging documentation. It meets EU Directive 2011/65/EU and IEC 61249-2-21:2011 standards. The "MTF" suffix denotes tape-and-reel packaging with lead-free (Pb-free) terminations and green molding compound - confirmed in Fairchild's original Rev. 1.1.0 datasheet and ON Semiconductor's current product status database.