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

onsemi BC639_D26Z

Name: BC639_D26Z
Brand: onsemi
SKU: BC639_D26Z
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BC639_D26Z

Manufacturer:: onsemi

Category:: Single Bipolar Transistors

Package:: TO-226-3, TO-92-3 (TO-226AA) Formed Leads

Datasheet:: BC639_D26Z.pdf

Description:: TRANS NPN 80V 1A TO-92-3

Quantity:: RFQ Add To RFQ list

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Product details

Overview

BC639_D26Z from ON Semiconductor (formerly Fairchild) is an NPN epitaxial silicon transistor designed for medium-power switching and linear amplification, with V_CEO = 80 V, I_C = 1 A, P_C = 1 W, h_FE ≥ 40 at I_C = 150 mA, and f_T = 100 MHz - used in relay drivers, power supply control stages, and audio preamplifiers.

For engineers reviewing the BC639_D26Z datasheet, pinout, applications, or equivalent options, key selection criteria include breakdown voltage margin, DC current gain consistency across operating current, saturation voltage at drive-relevant I_B/I_C ratios, thermal derating behavior in TO-92, and complementary pairing with BC640_D26Z.

Technical Context

This device operates as a general-purpose bipolar junction transistor with fixed-emitter configuration and base-controlled conduction. Its design supports both active-region amplification (V_CE ≥ 2 V, h_FE-driven biasing) and saturated-switching operation (V_CE(sat) ≤ 0.5 V at I_C = 500 mA, I_B = 50 mA).

It features low leakage (I_CBO ≤ 0.1 µA at V_CB = 30 V), stable gain over 5–500 mA collector current range, and junction temperature capability up to +150°C - enabling use in thermally constrained PCB layouts without forced cooling.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	80 V - maximum safe collector-emitter voltage before avalanche breakdown under open-base condition; defines upper rail limit in switch-mode topologies
I_C	1 A - continuous DC collector current rating; sets hard limit for steady-state load handling without thermal runaway
P_C	1 W - total package power dissipation at T_A = 25°C; requires derating above 25°C per specified slope (typically −8.3 mW/°C)
h_FE	40–160 - DC current gain at V_CE = 2 V, I_C = 150 mA; determines required base drive for target collector current
V_CE(sat)	0.5 V max at I_C = 500 mA, I_B = 50 mA - defines on-state power loss and minimum output swing in saturated switch applications
f_T	100 MHz - transition frequency at V_CE = 5 V, I_C = 10 mA; indicates usable bandwidth for small-signal amplification up to ~10 MHz

Pinout & Package

BC639_D26Z is housed in a standard TO-92 plastic package with 3 leads: Emitter (Lead 1), Collector (Lead 2), Base (Lead 3), oriented flat-side-up with leads down and left-to-right numbering.

Pin/Terminal	Circuit Role	Design Meaning
1 (Emitter)	Current exit path for majority carriers	Connected to circuit ground or low-impedance return; must handle full load current and support stable bias network referencing
2 (Collector)	Current entry path from supply/load	Interfaces with higher-voltage rails or inductive loads; requires layout clearance matching V_CEO rating and transient suppression if switching
3 (Base)	Control terminal for minority carrier injection	Driven by current-limited source; input impedance is low (~h_FE × r_e); sensitive to ESD and noise coupling

Key Features

Feature	Design Value
Complementary pairing	Matched performance with BC640_D26Z PNP for push-pull, differential, and H-bridge configurations
High V_CEO margin	80 V rating enables reliable operation in 48 V industrial bus and 24 V automotive auxiliary circuits
Low V_CE(sat)	≤ 0.5 V at rated I_C/I_B reduces conduction loss and self-heating in high-duty-cycle switching
Stable h_FE vs. I_C	Gain remains ≥40 from 5 mA to 500 mA, simplifying bias design across wide dynamic range

Applications

Relay Driver Stage	DC-DC Converter Switch
Use Scenario: Driving 12 V/500 mA electromagnetic relay coil from microcontroller GPIO. IC Role / Device Role / Timing Role: NPN switch providing current gain and isolation between logic-level control and inductive load. Use Value: V_CE(sat) ≤ 0.5 V minimizes coil voltage drop; h_FE ≥ 40 ensures sufficient drive with ≤12 mA base current.	Use Scenario: Low-side switching element in 5–24 V buck converter operating below 200 kHz. IC Role / Device Role / Timing Role: Power switch controlling energy transfer into output inductor during on-phase. Use Value: 80 V V_CEO provides headroom for flyback spikes; 1 A I_C supports up to 800 mA output with margin.
Audio Preamp Input Stage	Linear Voltage Regulator Pass Element
Use Scenario: First-stage low-noise amplifier for electret microphone signal conditioning. IC Role / Device Role / Timing Role: Common-emitter small-signal amplifier with emitter degeneration for gain stability. Use Value: f_T = 100 MHz ensures flat response beyond 20 kHz; low I_CBO avoids DC offset drift in high-Z bias networks.	Use Scenario: Series pass transistor in adjustable 3–15 V, 500 mA linear regulator with thermal foldback. IC Role / Device Role / Timing Role: Continuously biased current source regulating output voltage via feedback loop. Use Value: 150°C T_J(max) and 1 W P_C allow operation at 75°C ambient with 2.5 W dissipation using heatsink clip.

Relay Driver Stage

DC-DC Converter Switch

Use Scenario: Driving 12 V/500 mA electromagnetic relay coil from microcontroller GPIO.

IC Role / Device Role / Timing Role: NPN switch providing current gain and isolation between logic-level control and inductive load.

Use Value: V_CE(sat) ≤ 0.5 V minimizes coil voltage drop; h_FE ≥ 40 ensures sufficient drive with ≤12 mA base current.

Use Scenario: Low-side switching element in 5–24 V buck converter operating below 200 kHz.

IC Role / Device Role / Timing Role: Power switch controlling energy transfer into output inductor during on-phase.

Use Value: 80 V V_CEO provides headroom for flyback spikes; 1 A I_C supports up to 800 mA output with margin.

Audio Preamp Input Stage

Linear Voltage Regulator Pass Element

Use Scenario: First-stage low-noise amplifier for electret microphone signal conditioning.

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

Use Value: f_T = 100 MHz ensures flat response beyond 20 kHz; low I_CBO avoids DC offset drift in high-Z bias networks.

Use Scenario: Series pass transistor in adjustable 3–15 V, 500 mA linear regulator with thermal foldback.

IC Role / Device Role / Timing Role: Continuously biased current source regulating output voltage via feedback loop.

Use Value: 150°C T_J(max) and 1 W P_C allow operation at 75°C ambient with 2.5 W dissipation using heatsink clip.

Equivalent & Alternatives

The following parts are listed as comparable options for similar NPN switching and amplification applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
BC639-16	Same die, guaranteed h_FE = 100–250 (min 100) at I_C = 150 mA; tighter gain binning	Preferred where predictable base drive and consistent gain across production lots are critical	Select BC639-16 when h_FE variation must be bounded for analog gain-setting or precision current mirror use
MPSA42	Higher V_CEO = 300 V, lower I_C = 500 mA, smaller h_FE = 40–120, TO-92 compatible footprint	Suitable for higher-voltage but lower-current applications such as CRT deflection or telecom line interface	Choose MPSA42 only when >100 V breakdown is mandatory and 500 mA collector current suffices

Compared with BC639-16, BC639_D26Z offers broader h_FE tolerance (40–160) and lower cost for non-critical gain applications; versus MPSA42, it delivers higher current capacity and lower saturation voltage at the expense of reduced voltage rating - making BC639_D26Z optimal for 24–48 V, <1 A industrial switching.

Availability

BC639_D26Z is available at Aetrix Electronics and suitable for relay drivers, DC-DC converter switches, audio preamplifiers, and linear voltage regulator pass elements requiring stable component supply, long-term manufacturability, and legacy through-hole compatibility.

Supply support for BC639_D26Z 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 edge applications.

The BC639_D26Z belongs to Fairchild's legacy BC6xx family of general-purpose bipolar transistors, engineered for robustness, ease of use, and broad compatibility in discrete analog and power-switching designs.

FAQ

What is the pin configuration of BC639_D26Z?

The BC639_D26Z uses a TO-92 package with standardized pinout: Lead 1 = Emitter, Lead 2 = Collector, Lead 3 = Base - viewed with flat side facing outward and leads pointing downward, numbered left to right. This matches JEDEC TO-92 outline and is identical across BC635/637/639 variants.

Does BC639_D26Z have a guaranteed minimum hFE at high collector current?

Yes - BC639_D26Z guarantees h_FE ≥ 40 at V_CE = 2 V and I_C = 150 mA, and ≥ 25 at I_C = 500 mA. This ensures predictable base drive requirements in saturated switching applications where gain compression matters.

Can BC639_D26Z replace BC639 in existing designs?

Yes - BC639_D26Z is a direct replacement for BC639, sharing identical electrical specifications, TO-92 package, pinout, and thermal characteristics. The "_D26Z" suffix denotes tape-and-reel packaging and date/batch coding per ON Semiconductor's current marking convention.

What is the maximum safe operating temperature for BC639_D26Z?

The BC639_D26Z has a maximum junction temperature (T_J) of +150°C and storage temperature range of −65°C to +150°C. Derating begins at +25°C ambient, with typical thermal resistance R_θJA ≈ 200°C/W in still air - requiring heatsinking or airflow above ~500 mW dissipation.

Is BC639_D26Z suitable for audio amplifier applications?

Yes - BC639_D26Z is widely used in low-noise audio preamplifier stages due to its f_T = 100 MHz, low I_CBO (≤0.1 µA), and stable h_FE across 5–500 mA. Its performance supports full-audio-band amplification with proper biasing and emitter degeneration in common-emitter topology.

BC639_D26Z Specifications

Product attributes: Attribute value

Manufacturer:: onsemi

Series:: -

Package/Case:: TO-226-3, TO-92-3 (TO-226AA) Formed Leads

Packaging:: Tape & Reel (TR)

Product Status:: Obsolete

Transistor Type:: NPN

Current - Collector (Ic) (Max):: 1 A

Voltage - Collector Emitter Breakdown (Max):: 80 V

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

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

DC Current Gain (hFE) (Min) @ Ic, Vce:: 40 @ 150mA, 2V

Power - Max:: 1 W

Frequency - Transition:: 100MHz

Operating Temperature:: 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: TO-92-3

BC639_D26Z FAQ

1.How can I place an order for BC639_D26Z through Aetrix?

Please submit a Request for Quotation (RFQ) for BC639_D26Z 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 BC639_D26Z reliable?

The price and inventory of BC639_D26Z are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BC639_D26Z is usually 5 days.

3.What payment methods are accepted for BC639_D26Z?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BC639_D26Z transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BC639_D26Z?

BC639_D26Z orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BC639_D26Z 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 BC639_D26Z?

For technical support, including BC639_D26Z datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BC639_D26Z requirements.

6.How does Aetrix verify that BC639_D26Z is sourced from the original manufacturer or authorized distributors?

All BC639_D26Z 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 BC639_D26Z meets industry standards.

7.What is the process for return or replacement of BC639_D26Z?

All BC639_D26Z units undergo pre-shipment inspection (PSI). If there is an issue with BC639_D26Z, 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 BC639_D26Z part is unused and in its original packaging.

Return procedure for BC639_D26Z:

1.Submit a request within 90 days.

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

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