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

onsemi BCX19

Name: BCX19
Brand: onsemi
SKU: BCX19
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BCX19

Manufacturer:: onsemi

Category:: Single Bipolar Transistors

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

Datasheet:: BCX19.pdf

Description:: TRANS NPN 45V 0.5A SOT-23-3

Quantity:: RFQ Add To RFQ list

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Inventory:11,000

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Product details

Overview

BCX19 from NXP Semiconductors is an NPN general purpose transistor in SOT23 package, rated for 45 V V_CEO, 500 mA I_C, and 250 mW P_tot, used in saturated switching and low-power amplification circuits in consumer and industrial control modules.

For engineers reviewing the BCX19 datasheet, pinout, applications, or equivalent options, key selection criteria include DC current gain (h_FE = 100–600 at I_C = 100 mA), V_CE(sat) ≤ 620 mV at I_C = 500 mA / I_B = 50 mA, thermal resistance R_th(j-a) = 500 K/W, and SOT23 footprint compatibility.

Technical Context

The BCX19 operates as a silicon NPN bipolar junction transistor with base-controlled current amplification. Its design supports linear amplification at low collector currents and robust saturation switching up to 500 mA DC, with V_BE ≈ 1.2 V at I_C = 500 mA and V_CE = 1 V.

It features low collector capacitance (C_c ≤ 5 pF) and high transition frequency (f_T ≥ 100 MHz), enabling stable operation in audio-frequency amplifiers and digital logic interface drivers where bandwidth and switching speed are critical.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	45 V - maximum safe collector-emitter voltage under open-base condition, defining upper rail limit in switching applications
I_C	500 mA - continuous DC collector current rating, sets load-driving capability in relay or LED driver stages
h_FE	100–600 - DC current gain range at V_CE = 1 V and I_C = 100 mA, determines required base drive for saturation
V_CE(sat)	≤ 620 mV - collector-emitter voltage in full saturation at I_C = 500 mA / I_B = 50 mA, directly impacts power loss and heating
R_th(j-a)	500 K/W - junction-to-ambient thermal resistance on FR4 PCB, defines temperature rise per watt dissipated
f_T	≥ 100 MHz - transition frequency at I_C = 10 mA / V_CE = 5 V, indicates usable bandwidth for small-signal amplification

Pinout & Package

SOT23 plastic surface-mounted package (TO-236AB), 3-lead, 1.3 mm × 2.9 mm footprint, 1.1 mm height, designed for automated pick-and-place assembly and reflow soldering.

Pin/Terminal	Circuit Role	Design Meaning
1	Base	Current-controlled input node; requires ~50 mA base drive to saturate at 500 mA collector load
2	Emiter	Common reference terminal for NPN configuration; connected to ground or low-side return path
3	Collector	Output current sink terminal; handles up to 500 mA DC load with ≤620 mV drop in saturation

Key Features

Feature	Design Value
High DC current capability	500 mA continuous collector current enables direct driving of small relays, LEDs, and logic-level loads
Low saturation voltage	V_CE(sat) ≤ 620 mV at rated current minimizes conduction loss and self-heating in switching mode
Wide DC current gain range	h_FE = 100–600 allows flexible bias network design across production lots and temperature ranges
High-frequency response	f_T ≥ 100 MHz supports stable small-signal amplification up to mid-VHF band without compensation

Applications

Audio Pre-amplifier Stage	Microcontroller GPIO Driver
Use Scenario: Low-noise voltage amplification of line-level analog signals before ADC sampling in portable audio devices. IC Role / Device Role / Timing Role: NPN small-signal amplifier configured in common-emitter topology with emitter degeneration. Use Value: h_FE stability and f_T ≥ 100 MHz ensure flat gain response up to 20 kHz with minimal distortion.	Use Scenario: Level-shifting and current boosting of 3.3 V microcontroller output pins to drive 5 V TTL inputs or small solenoids. IC Role / Device Role / Timing Role: Saturated switch operating in cutoff/saturation modes controlled by MCU GPIO. Use Value: V_CE(sat) ≤ 620 mV and I_C = 500 mA rating enable reliable on/off control without external buffer ICs.
LED Current Sink	Industrial Sensor Interface
Use Scenario: Constant-current sinking of indicator or status LEDs in PLC I/O modules with 24 V supply rails. IC Role / Device Role / Timing Role: Linear or switched current sink with base resistor biasing for predictable LED brightness control. Use Value: 45 V V_CEO rating provides margin against transients on 24 V industrial buses.	Use Scenario: Signal conditioning and isolation interface between analog sensor outputs and 12-bit SAR ADC front-ends. IC Role / Device Role / Timing Role: Emitter-follower buffer providing low-output-impedance drive to ADC sample-and-hold capacitor. Use Value: High h_FE and low C_c ≤ 5 pF prevent loading-induced settling errors and phase lag.

Audio Pre-amplifier Stage

Microcontroller GPIO Driver

Use Scenario: Low-noise voltage amplification of line-level analog signals before ADC sampling in portable audio devices.

IC Role / Device Role / Timing Role: NPN small-signal amplifier configured in common-emitter topology with emitter degeneration.

Use Value: h_FE stability and f_T ≥ 100 MHz ensure flat gain response up to 20 kHz with minimal distortion.

Use Scenario: Level-shifting and current boosting of 3.3 V microcontroller output pins to drive 5 V TTL inputs or small solenoids.

IC Role / Device Role / Timing Role: Saturated switch operating in cutoff/saturation modes controlled by MCU GPIO.

Use Value: V_CE(sat) ≤ 620 mV and I_C = 500 mA rating enable reliable on/off control without external buffer ICs.

LED Current Sink

Industrial Sensor Interface

Use Scenario: Constant-current sinking of indicator or status LEDs in PLC I/O modules with 24 V supply rails.

IC Role / Device Role / Timing Role: Linear or switched current sink with base resistor biasing for predictable LED brightness control.

Use Value: 45 V V_CEO rating provides margin against transients on 24 V industrial buses.

Use Scenario: Signal conditioning and isolation interface between analog sensor outputs and 12-bit SAR ADC front-ends.

IC Role / Device Role / Timing Role: Emitter-follower buffer providing low-output-impedance drive to ADC sample-and-hold capacitor.

Use Value: High h_FE and low C_c ≤ 5 pF prevent loading-induced settling errors and phase lag.

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
BC817-40	Higher h_FE (250–630), same SOT23 package, V_CEO = 45 V, I_C = 500 mA, but lower R_th(j-a) = 375 K/W	Better thermal performance and tighter h_FE distribution; preferred for thermally constrained layouts	Select BC817-40 when improved thermal margin or tighter gain binning is required without changing PCB footprint
MMBT2222A	Higher V_CEO = 40 V (vs. BCX19's 45 V), same I_C = 600 mA, but higher V_CE(sat) ≈ 1 V at I_C = 500 mA	Widely available second-source; slightly higher saturation loss limits efficiency in high-duty-cycle switching	Choose MMBT2222A only if BCX19 is unavailable and system can tolerate ~380 mV higher V_CE(sat)

Compared with BCX19, BC817-40 offers superior thermal resistance and tighter h_FE spread for precision biasing, while MMBT2222A trades higher saturation voltage for broader global availability-neither is pin-compatible without validation of layout clearance and thermal pad requirements.

Availability

BCX19 is available at Aetrix Electronics and suitable for industrial control, consumer electronics, and automotive body electronics requiring stable component supply and long-term manufacturability.

Supply support for BCX19 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

NXP Semiconductors is a Dutch semiconductor company specializing in secure connectivity solutions for automotive, industrial, and IoT applications.

The BCX19 belongs to NXP's legacy general-purpose bipolar transistor product line, engineered for cost-sensitive, high-volume applications demanding reliability, consistent parametric performance, and SMT manufacturability.

FAQ

What is the maximum continuous collector current rating for BCX19?

The BCX19 has a maximum continuous collector current (I_C) rating of 500 mA at T_amb ≤ 25 °C. This rating assumes proper PCB thermal relief and derating above ambient temperatures; at 100 °C ambient, the usable I_C drops to approximately 250 mA due to thermal limitations. The BCX19 datasheet specifies this value under standard FR4 mounting conditions.

Is BCX19 suitable for linear amplification applications?

Yes, the BCX19 supports linear amplification with verified h_FE = 100–600 at V_CE = 1 V and I_C = 100 mA, and f_T ≥ 100 MHz. Its low collector capacitance (C_c ≤ 5 pF) and stable gain make it appropriate for audio pre-amplifier and signal-buffering stages where bandwidth up to 20 kHz is required. The BCX19 must be biased within its safe operating area to avoid thermal runaway.

What is the pin configuration of BCX19 in the SOT23 package?

The BCX19 uses standard SOT23 pinout: Pin 1 = Base, Pin 2 = Emitter, Pin 3 = Collector. This matches JEDEC TO-236AB outline and is consistent across NXP's BCX-series transistors. The marking code "U1" appears on the top surface, and orientation is confirmed by the device outline drawing in the BCX19 datasheet Figure 1.

Does BCX19 have a PNP complement part?

Yes, the PNP complement to BCX19 is BCX17, which shares identical SOT23 packaging, voltage ratings (V_CEO = −45 V), and current capability (I_C = −500 mA). Both parts are designed for complementary pair use in push-pull output stages or differential amplifiers, and their matching characteristics are documented in the respective NXP datasheets for BCX19 and BCX17.

What is the thermal resistance junction-to-ambient for BCX19?

The BCX19 has a thermal resistance R_th(j-a) of 500 K/W when mounted on a standard FR4 printed-circuit board with no copper pour. This value reflects worst-case convection-only cooling and must be used to calculate junction temperature rise: T_j = T_amb + (P_diss × 500). Derating curves in the BCX19 datasheet confirm safe operation up to 150 °C junction temperature.

BCX19 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):: 500 mA

Voltage - Collector Emitter Breakdown (Max):: 45 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:: 300 mW

Frequency - Transition:: -

Operating Temperature:: -55°C ~ 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: SOT-23-3

BCX19 FAQ

1.How can I place an order for BCX19 through Aetrix?

Please submit a Request for Quotation (RFQ) for BCX19 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 BCX19 reliable?

The price and inventory of BCX19 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BCX19 is usually 5 days.

3.What payment methods are accepted for BCX19?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BCX19 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BCX19?

BCX19 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BCX19 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 BCX19?

For technical support, including BCX19 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BCX19 requirements.

6.How does Aetrix verify that BCX19 is sourced from the original manufacturer or authorized distributors?

All BCX19 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 BCX19 meets industry standards.

7.What is the process for return or replacement of BCX19?

All BCX19 units undergo pre-shipment inspection (PSI). If there is an issue with BCX19, 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 BCX19 part is unused and in its original packaging.

Return procedure for BCX19:

1.Submit a request within 90 days.

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

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