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

onsemi BC639_D75Z

Name: BC639_D75Z
Brand: onsemi
SKU: BC639_D75Z
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BC639_D75Z

Manufacturer:: onsemi

Category:: Single Bipolar Transistors

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

Datasheet:: BC639_D75Z.pdf

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

Quantity:: RFQ Add To RFQ list

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Product details

Overview

BC639_D75Z from Fairchild Semiconductor is an NPN epitaxial silicon transistor designed for switching and amplifier applications, 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_D75Z datasheet, pinout, applications, or equivalent options, key selection factors include collector-emitter breakdown voltage, DC current gain at medium current, saturation voltage under 500 mA drive, thermal limits up to 150°C junction temperature, and TO-92 mechanical compatibility.

Technical Context

This device operates as a general-purpose NPN bipolar junction transistor with fixed emitter-base and collector-emitter voltage ratings defined per variant. Its h_FE is specified across three test conditions (5 mA, 150 mA, 500 mA), supporting both linear amplification and saturated switching roles.

The BC639_D75Z exhibits V_CE(sat) ≤ 0.5 V at I_C = 500 mA / I_B = 50 mA and V_BE(on) ≈ 1 V under same conditions, enabling predictable base drive design in low-to-medium power circuits without active bias compensation.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	80 V - maximum safe collector-emitter voltage before avalanche breakdown under open-base condition
I_C	1 A - continuous DC collector current rating defining steady-state power handling capability
P_C	1 W - total power dissipation limit at T_A = 25°C, requiring heatsinking above ~300 mW in enclosed environments
h_FE	≥40 at I_C = 150 mA - minimum DC current gain ensuring reliable switching with ≤3.75 mA base drive for 150 mA load
f_T	100 MHz - unity-gain bandwidth confirming usable small-signal amplification up to ~10–20 MHz with gain margin
V_CE(sat)	≤0.5 V at I_C = 500 mA, I_B = 50 mA - low saturation voltage minimizing conduction loss in switch-mode operation
T_J	150°C - maximum junction temperature permitting operation in industrial ambient up to 100°C with appropriate derating

Pinout & Package

BC639_D75Z is housed in a standard TO-92 plastic package with 3 leads: Emitter (Lead 1), Collector (Lead 2), Base (Lead 3), compliant with JEDEC TO-92 outline dimensions and lead spacing.

Pin/Terminal	Circuit Role	Design Meaning
1 (Emitter)	Current exit path for majority carriers	Connected to ground or low-side reference; requires low-impedance return path for stable biasing
2 (Collector)	Current entry path under forward-active or saturation mode	Typically tied to load or supply rail; handles full switched current and associated voltage transients
3 (Base)	Control terminal modulating collector current	Driven by resistor-limited voltage source; input impedance ~h_FE × r_e, sensitive to ESD during handling

Key Features

Feature	Design Value
High V_CEO rating	80 V enables use in 24–48 V industrial control rails without additional clamping components
Guaranteed h_FE at 150 mA	Ensures consistent switching behavior across production lots when driving relays or small solenoids
Low V_CE(sat)	Reduces power loss to ≤250 mW at 500 mA, easing thermal management in compact PCB layouts
TO-92 package compatibility	Supports manual assembly, wave soldering, and legacy socketing while maintaining industry-standard footprint
150°C junction rating	Allows operation in sealed enclosures or near heat sources where ambient exceeds 85°C

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 operating in saturation to fully energize relay with minimal voltage drop. Use Value: V_CE(sat) ≤ 0.5 V ensures >11.5 V delivered to coil, guaranteeing reliable pull-in even at low V_CC.	Use Scenario: Low-side switching element in 5–24 V buck converter feedback loop. IC Role / Device Role / Timing Role: Pulse-width controlled current sink regulating output voltage via duty cycle. Use Value: f_T = 100 MHz supports clean switching up to 500 kHz with low gate-drive overhead.
Audio Preamp Input Stage	Power Supply Enable Control
Use Scenario: First-stage common-emitter amplifier for line-level analog signals in battery-powered equipment. IC Role / Device Role / Timing Role: Linear amplifier biased in active region with fixed emitter degeneration. Use Value: h_FE ≥ 40 at 150 mA provides stable gain and low distortion across temperature range.	Use Scenario: Enabling/disabling auxiliary 5 V rail in multi-rail embedded system via MCU signal. IC Role / Device Role / Timing Role: High-side or low-side enable switch controlling PMOS/NMOS pass transistor gate. Use Value: I_C = 1 A rating accommodates inrush current of downstream capacitors without thermal stress.

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 operating in saturation to fully energize relay with minimal voltage drop.

Use Value: V_CE(sat) ≤ 0.5 V ensures >11.5 V delivered to coil, guaranteeing reliable pull-in even at low V_CC.

Use Scenario: Low-side switching element in 5–24 V buck converter feedback loop.

IC Role / Device Role / Timing Role: Pulse-width controlled current sink regulating output voltage via duty cycle.

Use Value: f_T = 100 MHz supports clean switching up to 500 kHz with low gate-drive overhead.

Audio Preamp Input Stage

Power Supply Enable Control

Use Scenario: First-stage common-emitter amplifier for line-level analog signals in battery-powered equipment.

IC Role / Device Role / Timing Role: Linear amplifier biased in active region with fixed emitter degeneration.

Use Value: h_FE ≥ 40 at 150 mA provides stable gain and low distortion across temperature range.

Use Scenario: Enabling/disabling auxiliary 5 V rail in multi-rail embedded system via MCU signal.

IC Role / Device Role / Timing Role: High-side or low-side enable switch controlling PMOS/NMOS pass transistor gate.

Use Value: I_C = 1 A rating accommodates inrush current of downstream capacitors without thermal stress.

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
BC639-10	Same die, binned h_FE = 100–300 (vs. BC639_D75Z's min 40); identical V_CEO, I_C, package	Preferred where higher and tighter h_FE tolerance required for gain-critical analog stages	Select BC639-10 only if circuit relies on precise current amplification; BC639_D75Z suffices for robust switching
MPSA42	V_CEO = 300 V, lower h_FE (min 40 at 10 mA), TO-92 compatible but higher V_CE(sat) (0.75 V)	Suitable for high-voltage flyback snubbers or AC line sensing where BC639_D75Z's 80 V is insufficient	Choose MPSA42 only when >100 V blocking is mandatory; avoid for low-loss switching due to higher saturation loss

Compared with BC639-10 and MPSA42, BC639_D75Z offers optimal balance of voltage rating, saturation performance, and cost for 24–48 V industrial switching - neither over-specified nor marginal in common relay and converter designs.

Availability

BC639_D75Z is available at Aetrix Electronics and suitable for relay driver circuits, DC-DC converter switches, and audio preamplifier stages requiring stable component supply, long-term obsolescence resilience, and TO-92 mechanical interchangeability.

Supply support for BC639_D75Z 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 U.S.-based semiconductor company specializing in power management, analog, and discrete devices before its acquisition by ON Semiconductor in 2016.

The BC639_D75Z belongs to Fairchild's BC63x family of general-purpose NPN transistors engineered for cost-sensitive industrial and consumer switching and amplification applications with standardized TO-92 packaging.

FAQ

What is the maximum collector-emitter voltage rating for BC639_D75Z?

The BC639_D75Z has a V_CEO rating of 80 V, meaning it can safely block up to 80 V between collector and emitter with the base open. This value is confirmed in the Absolute Maximum Ratings table under "VCEO Collector-Emitter Voltage" for the BC639 variant. Exceeding this voltage risks avalanche breakdown and permanent damage to the BC639_D75Z.

Does BC639_D75Z have a guaranteed DC current gain at high collector current?

Yes, BC639_D75Z guarantees h_FE ≥ 40 at V_CE = 2 V and I_C = 150 mA, as specified in the Electrical Characteristics table under "hFE2". This ensures predictable base drive requirements for medium-current switching applications such as relay coils or LED arrays, and is a key differentiator from lower-gain variants like BC635.

What is the typical saturation voltage of BC639_D75Z under rated switching conditions?

The BC639_D75Z exhibits V_CE(sat) ≤ 0.5 V when operated at I_C = 500 mA and I_B = 50 mA, per the datasheet's "Collector-Emitter Saturation Voltage" specification. This low saturation voltage minimizes power loss and self-heating during sustained on-state operation, making BC639_D75Z suitable for thermally constrained PCB layouts.

Is BC639_D75Z packaged in TO-92, and are pin assignments standardized?

Yes, BC639_D75Z uses the industry-standard TO-92 package with pinout: Lead 1 = Emitter, Lead 2 = Collector, Lead 3 = Base - matching JEDEC TO-92 outline drawings and verified in Fairchild's package dimension diagram. This ensures mechanical and soldering compatibility with existing TO-92 footprints and automated assembly tooling.

Can BC639_D75Z be used in audio amplifier circuits?

Yes, BC639_D75Z is qualified for linear amplification roles, including audio preamplifier input stages. Its h_FE stability across I_C = 5–500 mA and f_T = 100 MHz support bandwidth-limited small-signal gain with low distortion. For best results, operate BC639_D75Z within its specified V_CE and I_C derating curves to maintain linearity and thermal safety.

BC639_D75Z Specifications

Product attributes: Attribute value

Manufacturer:: onsemi

Series:: -

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

Packaging:: Tape & Box (TB)

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_D75Z FAQ

1.How can I place an order for BC639_D75Z through Aetrix?

Please submit a Request for Quotation (RFQ) for BC639_D75Z 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_D75Z reliable?

The price and inventory of BC639_D75Z are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BC639_D75Z is usually 5 days.

3.What payment methods are accepted for BC639_D75Z?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BC639_D75Z transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BC639_D75Z?

BC639_D75Z orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BC639_D75Z 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_D75Z?

For technical support, including BC639_D75Z datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BC639_D75Z requirements.

6.How does Aetrix verify that BC639_D75Z is sourced from the original manufacturer or authorized distributors?

All BC639_D75Z 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_D75Z meets industry standards.

7.What is the process for return or replacement of BC639_D75Z?

All BC639_D75Z units undergo pre-shipment inspection (PSI). If there is an issue with BC639_D75Z, 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_D75Z part is unused and in its original packaging.

Return procedure for BC639_D75Z:

1.Submit a request within 90 days.

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

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