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onsemi KST42MTF
- Part No.:
- KST42MTF
- Manufacturer:
- onsemi
- Category:
- Single Bipolar Transistors
- Package:
- TO-236-3, SC-59, SOT-23-3
- Datasheet:
-
KST42MTF.pdf
- Description:
- TRANS NPN 300V 0.5A SOT-23-3
- Quantity:
- Payment:
- Shipping:
Inventory:9,292
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Product details
Overview
KST42MTF from ON Semiconductor is a high-voltage NPN epitaxial silicon transistor in SOT-23 package, rated for 300 V collector-base and collector-emitter breakdown voltage, 500 mA continuous collector current, and 350 mW power dissipation. It serves as a switching or linear amplifier in high-voltage industrial power supplies and relay drivers.
For engineers reviewing the KST42MTF datasheet, pinout, applications, or equivalent options, key selection criteria include its 300 V BVCEO/BVCBO, low 0.5 V VCE(sat) at 20 mA/2 mA drive, 50 MHz fT, 3 pF Cob, and SOT-23 thermal resistance of 357 °C/W.
Technical Context
The KST42MTF is a discrete NPN bipolar junction transistor optimized for high-voltage switching applications where robustness against transient overvoltage is required. Its epitaxial base structure supports stable hFE (25–40) across 1–30 mA IC, with guaranteed VBE(sat) ≤ 0.9 V and VCE(sat) ≤ 0.5 V under defined drive conditions.
Thermal design is constrained by its SOT-23 package's 357 °C/W RθJA, requiring careful PCB copper area planning for >100 mW operation. The device exhibits low output capacitance (3 pF at VCB = 20 V), supporting fast turn-off in high-frequency switching circuits up to 50 MHz fT.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCBO / VCEO | 300 V - Enables use in 200–250 VAC line-sensing, flyback snubber, and relay coil suppression without derating. |
| IC (Continuous) | 500 mA - Supports medium-current switching loads such as solenoids, small motors, and LED strings. |
| VCE(sat) @ 20 mA/2 mA | 0.5 V - Minimizes conduction loss and self-heating during saturated switching in 5–24 V control circuits. |
| fT | 50 MHz - Allows stable operation in PWM frequencies up to ~5 MHz with adequate gain margin. |
| Cob | 3 pF @ VCB = 20 V - Reduces Miller effect and improves switching speed in high-dV/dt environments. |
| RθJA | 357 °C/W - Requires ≥25 mm² of 1-oz copper pad for safe 250 mW operation at TA = 70 °C. |
Pinout & Package
SOT-23 (TO-236AB) 3-lead plastic surface-mount package with gull-wing leads; JEDEC-compliant footprint (2.92 × 1.30 × 1.00 mm); moisture sensitivity level 1 (MSL-1).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (Base) | Current-controlled input node | Accepts 2 mA drive for full saturation; requires series resistor to limit IB and ensure hFE-based gain stability. |
| 2 (Emitter) | Reference terminal for bias and current return | Connected to system ground or low-side return path; must maintain low-impedance connection to minimize VBE error. |
| 3 (Collector) | High-voltage switched output node | Handles up to 300 V transient spikes; routed away from sensitive analog traces to avoid capacitive coupling. |
Key Features
| Feature | Design Value |
|---|---|
| High-voltage capability | 300 V BVCEO enables direct interface with 120/230 VAC-derived rails without external clamping. |
| Low saturation voltage | VCE(sat) ≤ 0.5 V at IC/IB = 20 mA/2 mA reduces power loss and thermal stress in repetitive switching. |
| Stable DC current gain | hFE = 25–40 across 1–30 mA IC ensures predictable base drive requirements in production designs. |
| Low output capacitance | Cob = 3 pF minimizes switching delay and EMI generation in high-dV/dt gate-drive or signal-switching roles. |
Applications
| Industrial Relay Drivers | AC Line Voltage Sensing |
|---|---|
Use Scenario: Driving 12–24 VDC coils of industrial electromechanical relays in PLC I/O modules. IC Role / Device Role / Timing Role: High-voltage NPN switch providing galvanically isolated coil energization via optocoupler-coupled base drive. Use Value: 300 V rating withstands inductive kickback up to 250 V without snubber, reducing BOM count and board space. |
Use Scenario: Zero-crossing detection and RMS voltage monitoring in smart energy meters and AC dimmers. IC Role / Device Role / Timing Role: High-impedance, high-voltage front-end switch sampling live AC phase with resistive divider scaling. Use Value: Low 0.1 μA ICBO ensures minimal leakage error at 230 VAC peak, improving measurement accuracy over temperature. |
| Flyback Converter Snubbers | High-Voltage LED String Switching |
Use Scenario: Clamping voltage spikes across transformer primary windings in offline flyback converters. IC Role / Device Role / Timing Role: Fast-turn-off NPN clamp transistor activated by RC network to absorb leakage inductance energy. Use Value: 50 MHz fT and 3 pF Cob enable sub-100 ns response, limiting VDS overshoot below MOSFET rating. |
Use Scenario: Series switching of multi-segment high-brightness LED strings in architectural lighting and signage. IC Role / Device Role / Timing Role: Medium-current, high-voltage series pass element controlling 100–200 V LED string current. Use Value: 500 mA IC and 350 mW PC support 350 mA constant-current drive with <100 mW dissipation at 200 V bus. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar high-voltage NPN transistor applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MMBT4401LT1G | Lower BVCEO = 40 V; higher hFE = 100–300; same SOT-23 package. | Not suitable for >60 V circuits; better for low-voltage logic-level switching with tighter gain tolerance. | Select only when operating voltage ≤ 30 V and high DC gain is prioritized over voltage rating. |
| ZTX450 | Higher BVCEO = 360 V; TO-92 package; PC = 1 W; slower fT ≈ 100 MHz. | Requires through-hole mounting and larger board area; superior thermal handling but lower frequency capability. | Choose for higher-power, lower-frequency applications where PCB real estate allows TO-92 and thermal mass is beneficial. |
Compared with MMBT4401LT1G and ZTX450, the KST42MTF uniquely balances 300 V rating, SOT-23 surface-mount compatibility, and 50 MHz bandwidth-making it optimal for compact, medium-power, high-voltage switching where both voltage headroom and layout density matter.
Availability
KST42MTF is available at Aetrix Electronics and suitable for industrial relay drivers, AC line sensing circuits, and flyback snubber networks requiring stable component supply with full traceability and lifecycle management.
Supply support for KST42MTF 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 and signal management solutions for automotive, industrial, cloud computing, and IoT applications.
The KST42MTF belongs to ON Semiconductor's legacy high-voltage bipolar transistor portfolio, originally developed by Fairchild for ruggedized industrial switching and voltage-tolerant interface circuits.
FAQ
What is the maximum continuous collector current for KST42MTF?
The KST42MTF supports a maximum continuous collector current of 500 mA at TA = 25 °C. Derating is required above 25 °C per the thermal resistance specification (RθJA = 357 °C/W); at 70 °C ambient, usable IC drops to approximately 350 mA with adequate PCB copper area.
Is KST42MTF pin-compatible with KST43MTF?
Yes, the KST42MTF and KST43MTF share identical SOT-23 pinout (Base–Emitter–Collector on pins 1–2–3) and mechanical footprint. However, KST43MTF has lower 200 V BVCEO/BVCBO ratings and is not interchangeable in 300 V applications without circuit redesign.
What is the typical DC current gain (hFE) of KST42MTF at 10 mA collector current?
The KST42MTF exhibits a typical hFE of 40 at VCE = 10 V and IC = 10 mA, with a minimum guaranteed value of 25 under the same conditions. This gain remains stable across IC = 1–30 mA, supporting consistent base drive design.
Can KST42MTF be used in linear amplifier configurations?
Yes, the KST42MTF can operate in linear mode with VCE between 1 V and 200 V, provided power dissipation stays within 350 mW and junction temperature remains ≤150 °C. Its low Cob and stable hFE support moderate-gain, high-input-impedance amplifier stages in HV signal conditioning.
Does KST42MTF have built-in ESD protection?
No, the KST42MTF does not integrate ESD protection diodes. Per the datasheet, it has standard HBM ESD rating of ±2 kV (Class N2), requiring external protection (e.g., series resistor + TVS) in handling-sensitive or field-deployed applications.
KST42MTF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- onsemi
- Series:
- -
- Package/Case:
- TO-236-3, SC-59, SOT-23-3
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- Transistor Type:
- NPN
- Current - Collector (Ic) (Max):
- 500 mA
- Voltage - Collector Emitter Breakdown (Max):
- 300 V
- Vce Saturation (Max) @ Ib, Ic:
- 500mV @ 2mA, 20mA
- Current - Collector Cutoff (Max):
- 100nA (ICBO)
- DC Current Gain (hFE) (Min) @ Ic, Vce:
- 40 @ 30mA, 10V
- Power - Max:
- 350 mW
- Frequency - Transition:
- 50MHz
- Operating Temperature:
- -55°C ~ 150°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- SOT-23-3
KST42MTF FAQ
1.How can I place an order for KST42MTF through Aetrix?
Please submit a Request for Quotation (RFQ) for KST42MTF on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for KST42MTF reliable?
The price and inventory of KST42MTF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for KST42MTF is usually 5 days.
3.What payment methods are accepted for KST42MTF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for KST42MTF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for KST42MTF?
KST42MTF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your KST42MTF order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for KST42MTF?
For technical support, including KST42MTF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your KST42MTF requirements.
6.How does Aetrix verify that KST42MTF is sourced from the original manufacturer or authorized distributors?
All KST42MTF products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that KST42MTF meets industry standards.
7.What is the process for return or replacement of KST42MTF?
All KST42MTF units undergo pre-shipment inspection (PSI). If there is an issue with KST42MTF, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The KST42MTF part is unused and in its original packaging.
Return procedure for KST42MTF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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