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

onsemi BC635_D27Z

Name: BC635_D27Z
Brand: onsemi
SKU: BC635_D27Z
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BC635_D27Z

Manufacturer:: onsemi

Category:: Single Bipolar Transistors

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

Datasheet:: BC635_D27Z.pdf

Description:: TRANS NPN 45V 1A TO-92-3

Quantity:: RFQ Add To RFQ list

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Product details

Overview

BC635_D27Z from Fairchild Semiconductor is an NPN epitaxial silicon transistor designed for general-purpose switching and linear amplification, with V_CEO = 45 V, I_C = 1 A, P_C = 1 W, h_FE ≥ 25 (at I_C = 5 mA), and f_T = 100 MHz - used in low-voltage relay drivers and audio preamplifier stages.

For engineers reviewing the BC635_D27Z datasheet, pinout, applications, or equivalent options, key selection considerations include its TO-92 package compatibility, DC current gain behavior across collector current range, saturation voltage at 500 mA drive, and complementary pairing with BC636_D27Z in push-pull configurations.

Technical Context

This NPN bipolar junction transistor operates in active, saturation, and cutoff regions with defined breakdown limits: V_CEO = 45 V, V_CER = 45 V (R_BE = 1 kΩ), and V_EBO = 5 V. Its h_FE varies from min. 25 at I_C = 5 mA to min. 40 at I_C = 150 mA, supporting both small-signal amplification and medium-current switching.

Thermal performance is characterized by T_J = 150°C maximum junction temperature and T_STG = –65 to 150°C storage range. The device 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 biasing in discrete amplifier and switch designs.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	45 V - maximum safe collector-emitter voltage before avalanche breakdown in open-base configuration
I_C	1 A - continuous collector current rating defining usable output drive capability
P_C	1 W - thermal power dissipation limit at T_A = 25°C, requiring heatsinking above ~300 mW in ambient
h_FE	25–250 - DC current gain range across operating points, critical for base drive sizing in switching circuits
f_T	100 MHz - unity-gain frequency indicating usable bandwidth up to ~10–20 MHz in common-emitter amplifiers
V_CE(sat)	≤ 0.5 V at I_C = 500 mA / I_B = 50 mA - ensures low conduction loss in saturated switch applications

Pinout & Package

BC635_D27Z is housed in a standard TO-92 plastic package with 3 leads: Emitter (Lead 1), Collector (Lead 2), Base (Lead 3), as confirmed by Fairchild's package drawing and pin identification diagram.

Pin/Terminal	Circuit Role	Design Meaning
1 (Emitter)	Current sink terminal	Reference node for bias network; connects to ground or low-side return path in common-emitter topology
2 (Collector)	Current source terminal	Drives load toward supply rail; requires external collector resistor or active pull-up in amplifier mode
3 (Base)	Control input terminal	Accepts current-limited drive signal; base resistor must be sized to ensure I_B ≥ I_C/h_FE(min) for saturation

Key Features

Feature	Design Value
Complementary pair availability	Directly paired with BC636_D27Z (PNP) for push-pull and differential amplifier use
High f_T bandwidth	100 MHz enables stable operation in audio-frequency amplifiers and fast-switching digital interfaces
Low V_CE(sat)	≤ 0.5 V reduces power loss and self-heating during high-duty-cycle switching
Wide h_FE range	25–250 supports robust design across production lots without recalculating base drive

Applications

Relay Driver Circuit	Audio Preamp Stage
Use Scenario: Driving 12 V/40 mA electromagnetic relay coil from microcontroller GPIO. IC Role / Device Role / Timing Role: NPN switch configured in common-emitter mode with base resistor and flyback diode. Use Value: V_CE(sat) ≤ 0.5 V minimizes coil voltage drop; h_FE ≥ 25 ensures full saturation with ≤ 20 mA base drive.	Use Scenario: First-stage voltage amplification in battery-powered portable audio mixer. IC Role / Device Role / Timing Role: Common-emitter amplifier biased at I_C = 5 mA with emitter degeneration resistor. Use Value: f_T = 100 MHz provides >20 MHz gain-bandwidth margin at 20 kHz audio band; low noise figure supports SNR > 85 dB.
LED Current Switch	Signal Level Shifter
Use Scenario: Controlling 350 mA white LED string from 3.3 V logic signal. IC Role / Device Role / Timing Role: Saturated switch with base resistor and current-limiting series resistor. Use Value: I_C = 1 A rating allows 350 mA operation with 3× thermal safety margin; P_C = 1 W accommodates 175 mW dissipation at 0.5 V × 350 mA.	Use Scenario: Translating 3.3 V logic output to 5 V TTL-compatible input in mixed-voltage MCU system. IC Role / Device Role / Timing Role: Common-emitter level shifter with pull-up to 5 V and base driven by 3.3 V source. Use Value: V_CEO = 45 V exceeds 5 V rail requirement; h_FE ≥ 25 ensures clean logic transition with <100 ns propagation delay.

Relay Driver Circuit

Audio Preamp Stage

Use Scenario: Driving 12 V/40 mA electromagnetic relay coil from microcontroller GPIO.

IC Role / Device Role / Timing Role: NPN switch configured in common-emitter mode with base resistor and flyback diode.

Use Value: V_CE(sat) ≤ 0.5 V minimizes coil voltage drop; h_FE ≥ 25 ensures full saturation with ≤ 20 mA base drive.

Use Scenario: First-stage voltage amplification in battery-powered portable audio mixer.

IC Role / Device Role / Timing Role: Common-emitter amplifier biased at I_C = 5 mA with emitter degeneration resistor.

Use Value: f_T = 100 MHz provides >20 MHz gain-bandwidth margin at 20 kHz audio band; low noise figure supports SNR > 85 dB.

LED Current Switch

Signal Level Shifter

Use Scenario: Controlling 350 mA white LED string from 3.3 V logic signal.

IC Role / Device Role / Timing Role: Saturated switch with base resistor and current-limiting series resistor.

Use Value: I_C = 1 A rating allows 350 mA operation with 3× thermal safety margin; P_C = 1 W accommodates 175 mW dissipation at 0.5 V × 350 mA.

Use Scenario: Translating 3.3 V logic output to 5 V TTL-compatible input in mixed-voltage MCU system.

IC Role / Device Role / Timing Role: Common-emitter level shifter with pull-up to 5 V and base driven by 3.3 V source.

Use Value: V_CEO = 45 V exceeds 5 V rail requirement; h_FE ≥ 25 ensures clean logic transition with <100 ns propagation delay.

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
BC635_T100Z	Same die, identical electrical specs, but tape-and-reel packaging (vs. bulk TO-92 for D27Z)	No functional difference; suited for automated SMT placement rather than manual/hand-soldered prototyping	Select BC635_T100Z only when feeding pick-and-place machines; BC635_D27Z remains optimal for lab builds and low-volume assembly.
PN2222A	V_CEO = 40 V (5 V lower), h_FE min = 100 at I_C = 10 mA, f_T = 300 MHz - higher gain and bandwidth but lower breakdown margin	Better for high-speed switching below 40 V; less suitable for 45 V tolerant designs or high-temperature environments where V_CEO derating applies	Choose PN2222A only if circuit operates ≤ 35 V and requires faster edge rates; retain BC635_D27Z for 45 V headroom and proven thermal stability at 150°C.

Compared with BC635_T100Z and PN2222A, BC635_D27Z offers the optimal balance of voltage margin, thermal robustness, and legacy design compatibility - especially where TO-92 bulk handling, 45 V operation, and documented Fairchild reliability are required.

Availability

BC635_D27Z is available at Aetrix Electronics and suitable for relay driver circuits, audio preamplifier stages, and LED current switching applications requiring stable component supply and long-term industrial availability.

Supply support for BC635_D27Z 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 analog and discrete semiconductor manufacturer, acquired by ON Semiconductor in 2016; known for high-reliability bipolar transistors and power devices.

The BC635_D27Z belongs to Fairchild's BC635/637/639 family of general-purpose NPN transistors, engineered for cost-effective, thermally stable switching and amplification in consumer, industrial, and automotive auxiliary systems.

FAQ

What is the maximum collector-emitter voltage rating for BC635_D27Z?

The BC635_D27Z has a V_CEO rating of 45 V - meaning it can safely block up to 45 V between collector and emitter with the base open. This value is confirmed in Fairchild's Rev. B2 datasheet under Absolute Maximum Ratings and Electrical Characteristics tables. Exceeding this voltage risks avalanche breakdown and permanent damage to the BC635_D27Z.

Is BC635_D27Z pin-compatible with BC636_D27Z?

Yes - BC635_D27Z (NPN) and BC636_D27Z (PNP) share identical TO-92 package dimensions and pinout: Emitter (1), Collector (2), Base (3). This complementary pairing is explicitly stated in the Fairchild datasheet and enables direct use in push-pull, phase-splitter, and differential amplifier circuits without layout changes for the BC635_D27Z.

What is the typical DC current gain (hFE) of BC635_D27Z at 5 mA collector current?

At V_CE = 2 V and I_C = 5 mA, the BC635_D27Z exhibits h_FE ranging from 25 (minimum) to 250 (typical), per Fairchild's datasheet. This wide gain spread reflects process variation and supports conservative base drive design - engineers should use h_FE(min) = 25 when calculating worst-case base resistor values for reliable saturation of the BC635_D27Z.

Does BC635_D27Z support switching at frequencies above 10 MHz?

The BC635_D27Z has an f_T of 100 MHz, indicating usable small-signal gain up to ~10–20 MHz depending on bias and load. While not optimized for RF, it reliably switches digital signals up to 5–10 MHz in properly designed common-emitter or emitter-follower configurations - verified via Fairchild's Figure 2 (h_FE vs. I_C) and Figure 5 (capacitance curves) in the BC635_D27Z datasheet.

What is the maximum power dissipation of BC635_D27Z at room temperature?

The BC635_D27Z has a rated collector power dissipation (P_C) of 1 W at T_A = 25°C, as specified in the Absolute Maximum Ratings table. This assumes free-air convection; actual usable power drops significantly with rising ambient temperature or lack of PCB copper area - for example, derated to ~500 mW at 70°C ambient. Thermal design must account for this limit to avoid exceeding T_J = 150°C in the BC635_D27Z.

BC635_D27Z 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):: 45 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

BC635_D27Z FAQ

1.How can I place an order for BC635_D27Z through Aetrix?

Please submit a Request for Quotation (RFQ) for BC635_D27Z 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 BC635_D27Z reliable?

The price and inventory of BC635_D27Z are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BC635_D27Z is usually 5 days.

3.What payment methods are accepted for BC635_D27Z?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BC635_D27Z transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BC635_D27Z?

BC635_D27Z orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BC635_D27Z 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 BC635_D27Z?

For technical support, including BC635_D27Z datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BC635_D27Z requirements.

6.How does Aetrix verify that BC635_D27Z is sourced from the original manufacturer or authorized distributors?

All BC635_D27Z 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 BC635_D27Z meets industry standards.

7.What is the process for return or replacement of BC635_D27Z?

All BC635_D27Z units undergo pre-shipment inspection (PSI). If there is an issue with BC635_D27Z, 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 BC635_D27Z part is unused and in its original packaging.

Return procedure for BC635_D27Z:

1.Submit a request within 90 days.

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

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