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

onsemi BCX70J

Name: BCX70J
Brand: onsemi
SKU: BCX70J
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BCX70J

Manufacturer:: onsemi

Category:: Single Bipolar Transistors

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

Datasheet:: BCX70J.pdf

Description:: TRANS NPN 45V 0.2A SOT-23-3

Quantity:: RFQ Add To RFQ list

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Product details

Overview

BCX70J from ON Semiconductor is an NPN epitaxial silicon general-purpose transistor in SOT-23 package, rated for 45 V V_CEO, 200 mA I_C, and 350 mW P_C, commonly used in low-power switching and amplification circuits in consumer electronics and industrial control interfaces.

For engineers reviewing the BCX70J datasheet, pinout, applications, or equivalent options, key selection considerations include its 125 MHz f_T, 40–460 h_FE range at multiple bias points, low 0.35 V V_CE(sat) at 10 mA/0.25 mA drive, and SOT-23 footprint compatibility with space-constrained PCB layouts.

Technical Context

The BCX70J operates as a discrete bipolar junction transistor with fixed NPN polarity and epitaxial base construction, supporting linear amplification and digital switching functions. Its DC current gain spans 40 to 460 depending on collector current (10 µA to 50 mA) and V_CE (1 V to 5 V), enabling flexible biasing across signal conditioning and load-driving stages.

It features 4.5 pF Cob output capacitance at 10 V V_CB, 6 dB noise figure at 1 kHz with 2 kΩ source resistance, and switching times of 150 ns t_ON and 800 ns t_OFF under defined test conditions-making it suitable for medium-speed digital logic interfacing and analog pre-amplifier stages.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	45 V - Maximum safe collector-emitter voltage before breakdown; defines upper rail limit in switching applications.
I_C	200 mA - Continuous collector current rating; sets maximum load drive capability without thermal derating.
P_C	350 mW - Power dissipation limit at T_A = 25°C; determines heatsinking requirements in ambient environments.
f_T	125 MHz - Unity-gain bandwidth; supports small-signal amplification up to ~10–20 MHz practical operating range.
h_FE	40–460 - DC current gain range across 10 µA–50 mA I_C; enables stable bias design in both low-current sensing and moderate-drive stages.
V_CE(sat)	0.35 V @ 10 mA/0.25 mA - Low saturation voltage reduces conduction loss in switch-mode operation.
C_ob	4.5 pF @ 10 V - Output junction capacitance; impacts high-frequency response and Miller effect in amplifier configurations.

Pinout & Package

SOT-23 plastic surface-mount package with gull-wing leads; 3-terminal configuration optimized for automated placement and reflow soldering on dense PCBs.

Pin/Terminal	Circuit Role	Design Meaning
1 (Base)	Control input terminal	Receives forward-biased current to enable conduction between collector and emitter; requires external current-limiting resistor in most driver applications.
2 (Emitter)	Current return path	Common reference node for bias network; typically grounded or connected to negative rail in common-emitter configurations.
3 (Collector)	Output current terminal	Delivers amplified or switched current to load; connects to positive supply or pull-up resistor in active-low switching topologies.

Key Features

Feature	Design Value
NPN epitaxial structure	Enables predictable gain behavior and improved high-frequency performance over diffused-base alternatives.
Low V_CE(sat) (0.35 V)	Reduces power loss and self-heating during saturated switching, improving efficiency in battery-powered systems.
Wide h_FE range (40–460)	Accommodates production variation and allows robust bias design across temperature and process corners.
125 MHz f_T	Supports audio-frequency amplification and medium-speed digital signal buffering without external compensation.
6 dB noise figure	Enables use in low-level analog front-end stages where signal integrity and SNR preservation are critical.

Applications

Audio Signal Amplification	Microcontroller GPIO Expansion
Use Scenario: Amplifying weak microphone or line-level signals in portable audio devices before ADC sampling. IC Role / Device Role / Timing Role: Small-signal NPN amplifier in common-emitter configuration with emitter degeneration for gain stability. Use Value: 125 MHz f_T and 6 dB noise figure ensure clean amplification up to 20 kHz with minimal added distortion.	Use Scenario: Driving LEDs, relays, or MOSFET gates from microcontroller I/O pins with limited current sourcing capability. IC Role / Device Role / Timing Role: Digital switch configured in common-emitter mode with base resistor limiting drive current. Use Value: 0.35 V V_CE(sat) minimizes voltage drop and power loss, preserving margin for downstream logic thresholds.
Industrial Sensor Interface	Power Supply Enable Control
Use Scenario: Level-shifting and current boosting for analog sensor outputs (e.g., thermistor bridges or current-loop transmitters). IC Role / Device Role / Timing Role: Linear amplifier or emitter-follower buffer isolating sensitive sensor circuitry from noisy load domains. Use Value: Wide h_FE range ensures consistent gain across unit-to-unit variation in factory-calibrated sensor modules.	Use Scenario: Enabling/disabling secondary voltage rails (e.g., 3.3 V or 5 V domains) via microcontroller command in multi-rail power systems. IC Role / Device Role / Timing Role: High-side or low-side switch controlling PMOS/NMOS gate drive or enable pin of DC-DC converters. Use Value: 45 V V_CEO rating provides headroom for transient spikes during rail sequencing and fault events.

Audio Signal Amplification

Microcontroller GPIO Expansion

Use Scenario: Amplifying weak microphone or line-level signals in portable audio devices before ADC sampling.

IC Role / Device Role / Timing Role: Small-signal NPN amplifier in common-emitter configuration with emitter degeneration for gain stability.

Use Value: 125 MHz f_T and 6 dB noise figure ensure clean amplification up to 20 kHz with minimal added distortion.

Use Scenario: Driving LEDs, relays, or MOSFET gates from microcontroller I/O pins with limited current sourcing capability.

IC Role / Device Role / Timing Role: Digital switch configured in common-emitter mode with base resistor limiting drive current.

Use Value: 0.35 V V_CE(sat) minimizes voltage drop and power loss, preserving margin for downstream logic thresholds.

Industrial Sensor Interface

Power Supply Enable Control

Use Scenario: Level-shifting and current boosting for analog sensor outputs (e.g., thermistor bridges or current-loop transmitters).

IC Role / Device Role / Timing Role: Linear amplifier or emitter-follower buffer isolating sensitive sensor circuitry from noisy load domains.

Use Value: Wide h_FE range ensures consistent gain across unit-to-unit variation in factory-calibrated sensor modules.

Use Scenario: Enabling/disabling secondary voltage rails (e.g., 3.3 V or 5 V domains) via microcontroller command in multi-rail power systems.

IC Role / Device Role / Timing Role: High-side or low-side switch controlling PMOS/NMOS gate drive or enable pin of DC-DC converters.

Use Value: 45 V V_CEO rating provides headroom for transient spikes during rail sequencing and fault events.

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
BC846B	Higher h_FE min (200 vs. 40), same SOT-23 package and 65 V V_CEO; slightly higher V_CE(sat) (0.4 V typical).	Better suited for low-base-drive applications; less tolerant of marginal base current in legacy designs.	Select BC846B when higher guaranteed gain is required and V_CEO margin above 45 V is beneficial.
MMBT3904	Identical pinout and core specs (40 V V_CEO, 200 mA I_C, 310 mW P_C); h_FE min 100, f_T 300 MHz.	Superior high-frequency response and tighter gain distribution; may require layout verification if noise or timing margins are critical.	Choose MMBT3904 for new designs prioritizing bandwidth and consistency; BCX70J remains valid for cost-sensitive or legacy-replacement use.

Compared with BCX70J, BC846B offers higher minimum gain but reduced saturation voltage margin, while MMBT3904 delivers significantly higher f_T and tighter h_FE spread-making it preferable for precision analog or faster-switching roles where BCX70J's broader gain tolerance is unnecessary.

Availability

BCX70J is available at Aetrix Electronics and suitable for industrial sensor interfaces, microcontroller peripheral driving, and portable audio signal conditioning requiring stable component supply and long-term obsolescence management.

Supply support for BCX70J 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 management, analog, sensors, and connectivity solutions for automotive, industrial, cloud, and consumer markets.

The BCX70J belongs to ON Semiconductor's legacy general-purpose transistor product line, originally developed by Fairchild and optimized for cost-effective, reliable discrete amplification and switching in high-volume electronics.

FAQ

What is the maximum collector-emitter voltage rating for BCX70J?

The BCX70J has a maximum collector-emitter voltage (V_CEO) rating of 45 V at T_A = 25°C. This rating applies under open-base conditions and must be derated linearly above 25°C ambient temperature per the device's thermal characteristics. Exceeding this voltage risks avalanche breakdown and permanent damage to the BCX70J junction.

Does BCX70J have a documented pinout configuration for SOT-23 package?

Yes, the BCX70J uses standard SOT-23 pinout: Pin 1 is Base, Pin 2 is Emitter, and Pin 3 is Collector. This configuration is confirmed in the official ON Semiconductor datasheet revision B2 (December 2002) and matches industry-standard SOT-23 orientation for NPN transistors. Always verify orientation using the device marking "AJ" and physical package notch.

What is the typical DC current gain (h_FE) range of BCX70J across operating conditions?

The BCX70J exhibits a DC current gain (h_FE) ranging from 40 to 460 depending on test conditions: minimum 40 at I_C = 10 µA, up to 250 at I_C = 2.0 mA, and 90–460 at I_C = 50 mA with V_CE = 1 V. This wide span reflects process variation and supports robust bias design across temperature and supply ranges in the BCX70J application.

Can BCX70J be used in high-frequency amplifier circuits?

The BCX70J has a current gain bandwidth product (f_T) of 125 MHz, making it suitable for audio-frequency amplification and medium-speed signal buffering. While not intended for RF or GHz-range operation, the BCX70J performs reliably in pre-amplifier stages up to ~20 MHz with proper layout and decoupling. Its 4.5 pF Cob and 6 dB noise figure further support fidelity-critical analog paths in the BCX70J application space.

Is BCX70J RoHS compliant and lead-free?

Yes, BCX70J is RoHS compliant and lead-free per ON Semiconductor's product change notifications and packaging documentation. The device meets EU Directive 2011/65/EU and subsequent amendments, with lead content below 0.1% by weight in homogeneous materials. Full compliance documentation, including substance declarations and test reports, is available through ON Semiconductor's quality portal for the BCX70J.

BCX70J 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):: 200 mA

Voltage - Collector Emitter Breakdown (Max):: 45 V

Vce Saturation (Max) @ Ib, Ic:: 550mV @ 1.25mA, 50mA

Current - Collector Cutoff (Max):: 20nA

DC Current Gain (hFE) (Min) @ Ic, Vce:: 250 @ 2mA, 5V

Power - Max:: 350 mW

Frequency - Transition:: 125MHz

Operating Temperature:: -

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: SOT-23-3

BCX70J FAQ

1.How can I place an order for BCX70J through Aetrix?

Please submit a Request for Quotation (RFQ) for BCX70J 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 BCX70J reliable?

The price and inventory of BCX70J are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BCX70J is usually 5 days.

3.What payment methods are accepted for BCX70J?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BCX70J transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BCX70J?

BCX70J orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BCX70J 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 BCX70J?

For technical support, including BCX70J datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BCX70J requirements.

6.How does Aetrix verify that BCX70J is sourced from the original manufacturer or authorized distributors?

All BCX70J 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 BCX70J meets industry standards.

7.What is the process for return or replacement of BCX70J?

All BCX70J units undergo pre-shipment inspection (PSI). If there is an issue with BCX70J, 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 BCX70J part is unused and in its original packaging.

Return procedure for BCX70J:

1.Submit a request within 90 days.

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

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