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Home > Products > Discrete Semiconductor Products > Transistors > Bipolar (BJT) > Single Bipolar Transistors

onsemi KST3904MTF

Name: KST3904MTF
Brand: onsemi
SKU: KST3904MTF
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: KST3904MTF

Manufacturer:: onsemi

Category:: Single Bipolar Transistors

Package:: TO-236-3, SC-59, SOT-23-3

Datasheet:: KST3904MTF.pdf

Description:: TRANS NPN 40V 0.2A SOT-23-3

Quantity:: RFQ Add To RFQ list

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Product details

Overview

KST3904MTF from ON Semiconductor (formerly Fairchild) is an NPN epitaxial silicon transistor in SOT-23 package, rated for 40 V V_CEO, 200 mA I_C, and 350 mW P_C; used in general-purpose switching and amplification circuits in power management, signal conditioning, and interface driver stages.

For engineers reviewing the KST3904MTF datasheet, pinout, applications, or equivalent options, key selection criteria include DC current gain (h_FE = 40–300 at I_C = 0.1–100 mA), low V_CE(sat) (0.2 V @ 10 mA/1 mA), f_T = 300 MHz, Cob = 4 pF, and SOT-23 thermal and layout compatibility.

Technical Context

This discrete NPN bipolar junction transistor operates in active, saturation, and cutoff regions with defined breakdown limits (V_CBO = 60 V, V_EBO = 6 V) and verified switching performance (t_ON = 70 ns, t_OFF = 250 ns under specified test conditions).

Its epitaxial base structure supports stable h_FE across collector currents from 0.1 mA to 100 mA, and its 4 pF output capacitance and 300 MHz f_T enable use in low-to-moderate frequency analog and digital switching applications up to ~100 MHz.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	40 V - Maximum safe collector-emitter voltage before breakdown in common-emitter configuration.
I_C	200 mA - Continuous DC collector current rating without derating at T_A = 25°C.
P_C	350 mW - Maximum power dissipation in SOT-23 package at ambient temperature.
h_FE	40–300 - DC current gain range across I_C = 0.1–100 mA, enabling predictable biasing in amplifier and switch designs.
f_T	300 MHz - Unity-gain bandwidth at V_CE = 20 V, I_C = 10 mA, supporting RF and high-speed digital switching.
V_CE(sat)	0.2 V @ 10 mA/1 mA - Low saturation voltage ensures minimal conduction loss in switching applications.
C_ob	4 pF @ V_CB = 5 V - Small output capacitance reduces Miller effect and improves high-frequency response.

Pinout & Package

SOT-23 plastic surface-mount package with gull-wing leads; compact footprint (2.90 mm × 1.30 mm × 1.00 mm max), optimized for automated assembly and thermal performance in space-constrained PCBs.

Pin/Terminal	Circuit Role	Design Meaning
1 (Base)	Control input	Receives base current to drive transistor into active or saturated region; requires current-limiting resistor in most configurations.
2 (Emitter)	Current return path	Common reference node for emitter-follower or grounded-emitter topologies; connected to GND or low-impedance return.
3 (Collector)	Output current sink	Delivers switched or amplified load current; routed to V_CC via load (e.g., LED, relay coil, logic gate input).

Key Features

Feature	Design Value
General-purpose NPN BJT	Validated for linear amplification and digital switching across industrial temperature range (−55°C to 150°C).
Low V_CE(sat)	0.2 V at I_C/I_B = 10 mA/1 mA enables efficient on-state operation in 3.3 V and 5 V logic-driven loads.
High f_T	300 MHz allows reliable use in pulse-width modulation (PWM) drivers, oscillator stages, and broadband preamplifiers.
Low noise figure	5 dB @ 100 μA, 5 V, 10 Hz–15.7 kHz supports audio and sensor-signal amplification where SNR matters.
SOT-23 footprint	Standardized 3-pin package ensures compatibility with existing pick-and-place equipment and reflow profiles.

Applications

LED Driver Circuits	Microcontroller Interface
Use Scenario: Driving indicator LEDs or small LED arrays from 3.3 V or 5 V MCU GPIO pins. IC Role / Device Role / Timing Role: NPN switch controlling current path to LED anode/cathode with base driven by microcontroller output. Use Value: Low V_CE(sat) minimizes voltage drop and heat generation; h_FE ≥ 70 at 1 mA ensures full saturation with typical GPIO drive capability.	Use Scenario: Level-shifting or signal inversion between mixed-voltage logic domains (e.g., 1.8 V MCU to 5 V peripheral). IC Role / Device Role / Timing Role: Discrete level translator using common-emitter configuration to invert and scale logic signals. Use Value: Fast t_ON/t_OFF (70/250 ns) supports >1 MHz digital signaling; SOT-23 size fits tight routing near microcontroller packages.
Power Supply Enable Switch	Audio Pre-amplifier Stage
Use Scenario: Enabling/disabling auxiliary rails (e.g., 12 V fan supply or sensor bias) via MCU-controlled switch. IC Role / Device Role / Timing Role: High-side or low-side power switch managing load current up to 200 mA. Use Value: 40 V V_CEO headroom accommodates transient spikes; 350 mW P_C supports continuous 100 mA loads at ambient temperatures ≤ 85°C.	Use Scenario: Low-noise voltage amplification of electret microphone or piezoelectric sensor outputs. IC Role / Device Role / Timing Role: Common-emitter small-signal amplifier with emitter degeneration for linearity and gain stability. Use Value: 5 dB noise figure and 300 MHz f_T preserve signal integrity in 20 Hz–20 kHz audio band; h_FE consistency simplifies bias network design.

LED Driver Circuits

Microcontroller Interface

Use Scenario: Driving indicator LEDs or small LED arrays from 3.3 V or 5 V MCU GPIO pins.

IC Role / Device Role / Timing Role: NPN switch controlling current path to LED anode/cathode with base driven by microcontroller output.

Use Value: Low V_CE(sat) minimizes voltage drop and heat generation; h_FE ≥ 70 at 1 mA ensures full saturation with typical GPIO drive capability.

Use Scenario: Level-shifting or signal inversion between mixed-voltage logic domains (e.g., 1.8 V MCU to 5 V peripheral).

IC Role / Device Role / Timing Role: Discrete level translator using common-emitter configuration to invert and scale logic signals.

Use Value: Fast t_ON/t_OFF (70/250 ns) supports >1 MHz digital signaling; SOT-23 size fits tight routing near microcontroller packages.

Power Supply Enable Switch

Audio Pre-amplifier Stage

Use Scenario: Enabling/disabling auxiliary rails (e.g., 12 V fan supply or sensor bias) via MCU-controlled switch.

IC Role / Device Role / Timing Role: High-side or low-side power switch managing load current up to 200 mA.

Use Value: 40 V V_CEO headroom accommodates transient spikes; 350 mW P_C supports continuous 100 mA loads at ambient temperatures ≤ 85°C.

Use Scenario: Low-noise voltage amplification of electret microphone or piezoelectric sensor outputs.

IC Role / Device Role / Timing Role: Common-emitter small-signal amplifier with emitter degeneration for linearity and gain stability.

Use Value: 5 dB noise figure and 300 MHz f_T preserve signal integrity in 20 Hz–20 kHz audio band; h_FE consistency simplifies bias network design.

Equivalent & Alternatives

The following parts are listed as comparable options for similar NPN general-purpose transistor applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
MMBT3904	Identical electrical specs and SOT-23 package; same h_FE range, V_CEO, f_T, and thermal ratings.	No functional difference; widely used interchangeably in switching and amplification roles.	Select MMBT3904 when sourcing from ON Semi's standard product line with identical traceability and qualification.
PN2222A	TO-92 package; higher P_C (1 W), lower f_T (250 MHz), and wider h_FE spread (100–300); not SOT-23 compatible.	Preferred for through-hole prototyping or higher-power linear operation where board space permits.	Choose PN2222A only if TO-92 mounting is required or thermal margin exceeds 350 mW in ambient conditions.

Compared with MMBT3904 and PN2222A, the KST3904MTF delivers identical small-signal NPN performance in SOT-23 with guaranteed 300 MHz f_T and low-noise capability-making it optimal for high-density, high-frequency, and low-voltage embedded designs where footprint and speed matter.

Availability

KST3904MTF is available at Aetrix Electronics and suitable for LED driver circuits, microcontroller interface translation, and power supply enable switching requiring stable component supply, consistent parametric performance, and SOT-23 manufacturability.

Supply support for KST3904MTF 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 KST3904MTF belongs to ON Semiconductor's general-purpose bipolar transistor product line, designed for cost-sensitive, high-volume switching and amplification tasks in consumer, computing, and industrial control systems.

FAQ

What is the maximum collector-emitter voltage rating for KST3904MTF?

The KST3904MTF has a maximum collector-emitter voltage (V_CEO) rating of 40 V at T_A = 25°C. This rating defines the upper limit of voltage that can be safely applied between collector and emitter with the base open. Exceeding this value risks avalanche breakdown and permanent device failure. Derating is required above 25°C ambient per the datasheet thermal curves.

Does KST3904MTF support switching at 1 MHz?

Yes, the KST3904MTF supports reliable switching at 1 MHz due to its 300 MHz current gain-bandwidth product (f_T) and fast switching times (t_ON = 70 ns, t_OFF = 250 ns). At 1 MHz, duty cycle and load impedance must be selected to keep average power within 350 mW and junction temperature below 150°C. Layout parasitics should be minimized to maintain edge fidelity.

Is KST3904MTF pin-compatible with MMBT3904?

Yes, the KST3904MTF is pin-compatible with MMBT3904: both use SOT-23 package with identical pinout (1 = Base, 2 = Emitter, 3 = Collector) and match in mechanical dimensions, solder pad layout, and thermal profile. Electrical parameters-including V_CEO, h_FE, V_CE(sat), and f_T-are identical per official ON Semiconductor documentation.

What is the minimum h_FE guaranteed for KST3904MTF at I_C = 10 mA?

The minimum DC current gain (h_FE) guaranteed for KST3904MTF at V_CE = 1 V and I_C = 10 mA is 100, per the "Electrical Characteristics" table in the official datasheet. This value ensures predictable base drive requirements in amplifier and switch bias networks, and applies across the full operating temperature range (−55°C to 150°C) unless otherwise specified.

Can KST3904MTF be used in audio preamplifier applications?

Yes, the KST3904MTF is suitable for low-noise audio preamplifier applications, with a specified noise figure of 5 dB at I_C = 100 μA, V_CE = 5 V, R_S = 1 kΩ, and 10 Hz–15.7 kHz bandwidth. Its h_FE stability and 300 MHz f_T support faithful amplification of voice- and music-band signals when configured in common-emitter or emitter-follower topologies with proper biasing.

KST3904MTF Specifications

Product attributes: Attribute value

Manufacturer:: onsemi

Series:: -

Package/Case:: TO-236-3, SC-59, SOT-23-3

Packaging:: Bulk

Product Status:: Active

Transistor Type:: NPN

Current - Collector (Ic) (Max):: 200 mA

Voltage - Collector Emitter Breakdown (Max):: 40 V

Vce Saturation (Max) @ Ib, Ic:: 300mV @ 5mA, 50mA

Current - Collector Cutoff (Max):: -

DC Current Gain (hFE) (Min) @ Ic, Vce:: 100 @ 10mA, 1V

Power - Max:: 350 mW

Frequency - Transition:: 300MHz

Operating Temperature:: -

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: SOT-23-3

KST3904MTF FAQ

1.How can I place an order for KST3904MTF through Aetrix?

Please submit a Request for Quotation (RFQ) for KST3904MTF 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 KST3904MTF reliable?

The price and inventory of KST3904MTF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for KST3904MTF is usually 5 days.

3.What payment methods are accepted for KST3904MTF?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for KST3904MTF transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for KST3904MTF?

KST3904MTF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your KST3904MTF 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 KST3904MTF?

For technical support, including KST3904MTF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your KST3904MTF requirements.

6.How does Aetrix verify that KST3904MTF is sourced from the original manufacturer or authorized distributors?

All KST3904MTF 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 KST3904MTF meets industry standards.

7.What is the process for return or replacement of KST3904MTF?

All KST3904MTF units undergo pre-shipment inspection (PSI). If there is an issue with KST3904MTF, 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 KST3904MTF part is unused and in its original packaging.

Return procedure for KST3904MTF:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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