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

onsemi BCX20

Name: BCX20
Brand: onsemi
SKU: BCX20
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BCX20

Manufacturer:: onsemi

Category:: Single Bipolar Transistors

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

Datasheet:: BCX20.pdf

Description:: TRANS NPN 25V 0.8A SOT-23-3

Quantity:: RFQ Add To RFQ list

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Product details

Overview

BCX20 from Fairchild Semiconductor is an NPN epitaxial silicon transistor designed for switching and amplifier applications, with V_CEO = 25 V, I_C = 800 mA, P_C = 310 mW, h_FE = 100–600 at I_C = 100–500 mA, and SOT-23 package. It operates reliably in consumer audio preamps, relay drivers, and low-power logic interface circuits.

For engineers reviewing the BCX20 datasheet, pinout, applications, or equivalent options, key selection considerations include its DC current gain range across operating currents, V_CE(sat) of 0.62 V at I_C = 500 mA / I_B = 50 mA, thermal limits up to T_J = 150°C, and SOT-23 footprint compatibility with space-constrained PCB layouts.

Technical Context

The BCX20 is a general-purpose NPN bipolar junction transistor optimized for linear amplification and saturated switching. Its h_FE varies predictably with collector current-100–600 at 100–500 mA-and exhibits low V_CE(sat) (0.62 V) and V_BE(on) (1.2 V) under rated drive conditions.

It features epitaxial base construction for improved frequency response and consistency, with breakdown ratings of V_CES = 30 V and V_EBO = 5 V. Leakage currents are tightly controlled: I_CBO ≤ 100 nA at V_CE = 20 V and I_EBO ≤ 10 nA at V_BE = 5 V.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	25 V - Maximum safe collector-emitter voltage under open-base condition; defines upper rail limit in switching designs.
I_C	800 mA - Absolute maximum continuous DC collector current; sets peak load capability before thermal derating.
P_C	310 mW - Maximum power dissipation at T_A = 25°C in SOT-23; requires thermal design for >150°C junction operation.
h_FE	100–600 - DC current gain range across I_C = 100–500 mA; enables stable biasing in amplifier and switch driver stages.
V_CE(sat)	0.62 V - Collector-emitter saturation voltage at I_C = 500 mA / I_B = 50 mA; determines conduction loss in saturated-switch applications.
T_J	150°C - Maximum junction temperature; supports operation in sealed enclosures or elevated ambient environments.

Pinout & Package

SOT-23 plastic surface-mount package with gull-wing leads; compact 2.9 mm × 1.3 mm footprint and 1.0 mm height; marked "U2".

Pin/Terminal	Circuit Role	Design Meaning
1	Base	Current-controlled input node; requires series resistor to limit I_B and ensure proper h_FE-based gain control.
2	Emitter	Common reference terminal; tied to ground or low-side return path in common-emitter configurations.
3	Collector	Output current sink node; connects to load (e.g., relay coil, LED string, or next-stage input) in switching applications.

Key Features

Feature	Design Value
Epitaxial base structure	Enables consistent h_FE and improved f_T stability across production lots and temperature ranges.
Low V_CE(sat)	0.62 V at rated I_C/I_B reduces power loss and self-heating in high-duty-cycle switching.
High h_FE range	100–600 supports both precision biasing in analog stages and robust overdrive in digital interface circuits.
Low leakage	I_CBO ≤ 100 nA ensures minimal standby current in battery-powered or always-on signal paths.

Applications

Audio Preamp Stage	Relay Driver Circuit
Use Scenario: Low-noise small-signal amplification in portable microphone or line-level input stages. IC Role / Device Role / Timing Role: NPN transistor configured in common-emitter topology for voltage gain and impedance transformation. Use Value: h_FE ≥ 100 at I_C = 100 mA ensures stable gain without excessive base drive, while low I_CBO preserves signal integrity.	Use Scenario: Driving 12 V/400 mA electromagnetic relays from microcontroller GPIO pins. IC Role / Device Role / Timing Role: Saturated switch controlling relay coil current with fast turn-on/turn-off via base overdrive. Use Value: V_CE(sat) = 0.62 V minimizes coil voltage drop and power dissipation; SOT-23 allows dense layout near MCU.
Logic Level Translator	LED Current Switch
Use Scenario: Interfacing 3.3 V FPGA outputs to 5 V peripheral enable lines. IC Role / Device Role / Timing Role: Single-transistor level shifter using emitter-follower or common-emitter inversion as needed. Use Value: V_EBO = 5 V permits safe base-emitter reverse bias during level transitions; h_FE > 70 ensures reliable switching at 10 mA output loads.	Use Scenario: Constant-current switching of indicator LEDs in industrial HMI panels. IC Role / Device Role / Timing Role: Low-side current sink with fixed base resistor defining LED current via h_FE and V_CE(sat). Use Value: Tight V_CE(sat) tolerance ensures predictable LED brightness; T_J = 150°C rating supports operation in sealed metal enclosures.

Audio Preamp Stage

Relay Driver Circuit

Use Scenario: Low-noise small-signal amplification in portable microphone or line-level input stages.

IC Role / Device Role / Timing Role: NPN transistor configured in common-emitter topology for voltage gain and impedance transformation.

Use Value: h_FE ≥ 100 at I_C = 100 mA ensures stable gain without excessive base drive, while low I_CBO preserves signal integrity.

Use Scenario: Driving 12 V/400 mA electromagnetic relays from microcontroller GPIO pins.

IC Role / Device Role / Timing Role: Saturated switch controlling relay coil current with fast turn-on/turn-off via base overdrive.

Use Value: V_CE(sat) = 0.62 V minimizes coil voltage drop and power dissipation; SOT-23 allows dense layout near MCU.

Logic Level Translator

LED Current Switch

Use Scenario: Interfacing 3.3 V FPGA outputs to 5 V peripheral enable lines.

IC Role / Device Role / Timing Role: Single-transistor level shifter using emitter-follower or common-emitter inversion as needed.

Use Value: V_EBO = 5 V permits safe base-emitter reverse bias during level transitions; h_FE > 70 ensures reliable switching at 10 mA output loads.

Use Scenario: Constant-current switching of indicator LEDs in industrial HMI panels.

IC Role / Device Role / Timing Role: Low-side current sink with fixed base resistor defining LED current via h_FE and V_CE(sat).

Use Value: Tight V_CE(sat) tolerance ensures predictable LED brightness; T_J = 150°C rating supports operation in sealed metal enclosures.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
BC817-40	Higher h_FE min = 250 at I_C = 100 mA; same SOT-23, V_CEO = 45 V, P_C = 310 mW	Better suited for low-drive amplifier stages where higher gain margin is required	Select BC817-40 when designing for lower base current or tighter h_FE consistency across temperature
MMBT2222A	V_CEO = 40 V, h_FE = 100–300 at I_C = 150 mA, V_CE(sat) = 0.6–1.2 V (wider spread), same SOT-23	Broader V_CEO margin but less predictable saturation behavior at high I_C	Choose MMBT2222A only if higher voltage headroom is critical and V_CE(sat) variation is acceptable

Compared with BCX20, BC817-40 offers higher guaranteed h_FE for reduced base drive sensitivity, while MMBT2222A trades tighter V_CE(sat) control for greater voltage tolerance-making BCX20 optimal for cost-sensitive, thermally constrained 25 V switching where gain and saturation voltage predictability are prioritized.

Availability

BCX20 is available at Aetrix Electronics and suitable for audio preamplifiers, relay drivers, logic level translators, and LED current switches requiring stable component supply and long-term manufacturability.

Supply support for BCX20 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

Fairchild Semiconductor was a leading designer and manufacturer of power management, analog, and discrete semiconductor solutions, acquired by ON Semiconductor in 2016.

The BCX20 belongs to Fairchild's legacy general-purpose bipolar transistor family, engineered for cost-effective, reliable switching and amplification in consumer, industrial, and computing applications.

FAQ

What is the maximum collector current rating for BCX20?

The BCX20 has an absolute maximum DC collector current (I_C) rating of 800 mA at T_A = 25°C. However, sustained operation above 500 mA requires careful thermal management due to its 310 mW power dissipation limit in the SOT-23 package. Derating curves in the BCX20 datasheet define safe operating area boundaries based on ambient temperature and PCB copper area.

Does BCX20 have a specified transition frequency (f_T)?

No, the official BCX20 Rev. A datasheet from Fairchild Semiconductor does not specify transition frequency (f_T). It is characterized for DC and low-frequency switching/amplifier use, with performance validated up to audio frequencies. For RF or high-speed switching applications, designers should select transistors explicitly rated for f_T, such as the MMBTH10 or PN2222A variants.

What is the pin configuration of BCX20 in the SOT-23 package?

The BCX20 uses standard SOT-23 pinout: Pin 1 is Base, Pin 2 is Emitter, and Pin 3 is Collector-verified in the mechanical drawing section of the BCX20 Rev. A datasheet. The device is marked "U2" on the top surface, and orientation follows JEDEC MO-178 with the marking dot indicating Pin 1.

Can BCX20 replace BC547 in existing designs?

BCX20 is not a direct replacement for BC547 due to differences in package (SOT-23 vs. TO-92), pinout, and electrical profile: BC547 has V_CEO = 45 V and h_FE = 110–800, while BCX20 has V_CEO = 25 V and lower max h_FE. Substitution requires PCB layout change and validation of gain, saturation, and thermal margins in the BCX20's SOT-23 footprint.

Is BCX20 suitable for automotive applications?

The BCX20 is not qualified to AEC-Q101 or automotive-grade reliability standards. Its datasheet specifies operation from –65°C to +150°C storage, but no automotive qualification testing, PPAP documentation, or failure-in-time (FIT) data is provided. For automotive use, consider AEC-Q101 qualified alternatives like the NSVBCX20LT1G or MMBT2222AL.

BCX20 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):: 800 mA

Voltage - Collector Emitter Breakdown (Max):: 25 V

Vce Saturation (Max) @ Ib, Ic:: 620mV @ 50mA, 500mA

Current - Collector Cutoff (Max):: 100nA (ICBO)

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

Power - Max:: 310 mW

Frequency - Transition:: -

Operating Temperature:: 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: SOT-23-3

BCX20 FAQ

1.How can I place an order for BCX20 through Aetrix?

Please submit a Request for Quotation (RFQ) for BCX20 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 BCX20 reliable?

The price and inventory of BCX20 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BCX20 is usually 5 days.

3.What payment methods are accepted for BCX20?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BCX20 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BCX20?

BCX20 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BCX20 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 BCX20?

For technical support, including BCX20 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BCX20 requirements.

6.How does Aetrix verify that BCX20 is sourced from the original manufacturer or authorized distributors?

All BCX20 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 BCX20 meets industry standards.

7.What is the process for return or replacement of BCX20?

All BCX20 units undergo pre-shipment inspection (PSI). If there is an issue with BCX20, 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 BCX20 part is unused and in its original packaging.

Return procedure for BCX20:

1.Submit a request within 90 days.

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

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