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

onsemi BC638TF

Name: BC638TF
Brand: onsemi
SKU: BC638TF
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BC638TF

Manufacturer:: onsemi

Category:: Single Bipolar Transistors

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

Datasheet:: BC638TF.pdf

Description:: TRANS PNP 60V 1A TO-92-3

Quantity:: RFQ Add To RFQ list

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Inventory:9,991

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Product details

Overview

BC638TF from onsemi is a PNP epitaxial silicon transistor designed for medium-power switching and linear amplification, with V_CEO = −60 V, I_C = −1 A, h_FE = 25–160 (at I_C = −5 mA to −500 mA), V_CE(sat) = −0.5 V (at I_C = −500 mA, I_B = −50 mA), and f_T = 100 MHz - used in relay drivers, power supply control stages, and discrete amplifier output stages.

For engineers reviewing the BC638TF datasheet, pinout, applications, or equivalent options, key selection criteria include its TO-92-3 package compatibility, complementary pairing with BC637, Pb-free/RoHS compliance, and verified DC gain behavior across collector current range from 5 mA to 500 mA.

Technical Context

This PNP bipolar junction transistor operates with reverse-polarity biasing: emitter positive relative to base and collector. Its breakdown ratings (V_CEO, V_CER, V_CES) are all −60 V, and it supports peak pulsed current up to −1.5 A with thermal resistance R_JA = 125 °C/W on standard FR-4 PCB.

DC current gain exhibits strong current dependency: h_FE = 25 at I_C = −5 mA, rises to 40–160 at I_C = −150 mA, then drops to 25 again at I_C = −500 mA - indicating optimized mid-current operation and saturation voltage stability under switching loads.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	−60 V: Maximum safe collector-emitter voltage before avalanche breakdown in open-base configuration.
I_C	−1 A continuous: Sustained collector current rating defining usable power-handling capacity in linear or switching mode.
h_FE	25–160: DC current gain range across operating currents, enabling predictable base drive sizing for switching or amplification.
V_CE(sat)	−0.5 V at I_C = −500 mA / I_B = −50 mA: Low saturation voltage ensures minimal conduction loss in saturated-switch applications.
f_T	100 MHz: Transition frequency confirming usable bandwidth for audio-frequency amplification and fast digital switching.
P_D	1 W at T_A = 25°C: Power dissipation limit requiring thermal derating (8 mW/°C) above ambient for reliable operation.

Pinout & Package

BC638TF is housed in a TO-92-3 plastic package (Case 135AR), lead-formed, with standardized pin assignment: Pin 1 = Emitter, Pin 2 = Collector, Pin 3 = Base - compatible with manual soldering and through-hole PCB assembly.

Pin/Terminal	Circuit Role	Design Meaning
1 (Emitter)	Current source terminal in PNP operation	Connected to higher potential rail; base-emitter forward bias initiates conduction.
2 (Collector)	Current sink terminal	Drains load current to lower potential; voltage swing limited by V_CEO = −60 V.
3 (Base)	Control input for minority-carrier injection	Requires negative current relative to emitter to turn on; I_B ≤ −100 mA absolute max.

Key Features

Feature	Design Value
Complementary pairing	Designed as direct PNP counterpart to NPN BC637, enabling matched push-pull or differential stage implementation.
RoHS-compliant construction	Pb-free, halogen-free/BFR-free packaging meets global environmental compliance requirements without performance trade-offs.
Medium-power switching capability	Rated for −1 A continuous and −1.5 A peak collector current with stable V_CE(sat) under high-current drive.
Wide h_FE operating range	Supports both low-current signal amplification (h_FE = 25 at 5 mA) and high-current switching (h_FE = 40–160 at 150 mA).

Applications

Relay Driver Circuit	Linear Voltage Regulator Pass Element
Use Scenario: Driving electromagnetic relays requiring ≥500 mA coil current with TTL/CMOS-compatible base drive. IC Role / Device Role / Timing Role: PNP switch controlling relay coil ground path; emitter tied to V_CC, collector to coil, base driven via current-limiting resistor. Use Value: V_CE(sat) = −0.5 V minimizes power loss and heat rise during sustained relay activation.	Use Scenario: Discrete pass transistor in adjustable linear regulators delivering up to 1 A output current. IC Role / Device Role / Timing Role: Series-pass element regulating output voltage via base voltage control from error amplifier feedback loop. Use Value: h_FE stability across 5–500 mA enables consistent regulation accuracy and thermal predictability.
DC Motor Direction Control (Half-Bridge)	Audio Preamp Output Stage
Use Scenario: High-side switch in H-bridge motor driver for bidirectional 12 V DC motor control. IC Role / Device Role / Timing Role: Upper PNP switch sourcing current to motor terminal; paired with NPN low-side switch for polarity reversal. Use Value: −60 V V_CEO provides margin against inductive kickback during motor commutation.	Use Scenario: Class-A output stage in low-noise audio preamplifiers targeting <1% THD at 1 kHz. IC Role / Device Role / Timing Role: Emitter-follower buffer delivering low-impedance drive to headphones or next-stage inputs. Use Value: f_T = 100 MHz ensures flat frequency response beyond 20 kHz with minimal phase shift.

Relay Driver Circuit

Linear Voltage Regulator Pass Element

Use Scenario: Driving electromagnetic relays requiring ≥500 mA coil current with TTL/CMOS-compatible base drive.

IC Role / Device Role / Timing Role: PNP switch controlling relay coil ground path; emitter tied to V_CC, collector to coil, base driven via current-limiting resistor.

Use Value: V_CE(sat) = −0.5 V minimizes power loss and heat rise during sustained relay activation.

Use Scenario: Discrete pass transistor in adjustable linear regulators delivering up to 1 A output current.

IC Role / Device Role / Timing Role: Series-pass element regulating output voltage via base voltage control from error amplifier feedback loop.

Use Value: h_FE stability across 5–500 mA enables consistent regulation accuracy and thermal predictability.

DC Motor Direction Control (Half-Bridge)

Audio Preamp Output Stage

Use Scenario: High-side switch in H-bridge motor driver for bidirectional 12 V DC motor control.

IC Role / Device Role / Timing Role: Upper PNP switch sourcing current to motor terminal; paired with NPN low-side switch for polarity reversal.

Use Value: −60 V V_CEO provides margin against inductive kickback during motor commutation.

Use Scenario: Class-A output stage in low-noise audio preamplifiers targeting <1% THD at 1 kHz.

IC Role / Device Role / Timing Role: Emitter-follower buffer delivering low-impedance drive to headphones or next-stage inputs.

Use Value: f_T = 100 MHz ensures flat frequency response beyond 20 kHz with minimal phase shift.

Equivalent & Alternatives

The following parts are listed as comparable options for similar PNP medium-power transistor applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
BC638TA	Same die, identical electrical specs; differs only in lead form (straight vs. bent leads) and packaging (fan-fold vs. bulk).	No functional difference; choice depends solely on assembly process (auto-insertion vs. hand-soldering).	Select BC638TA for automated through-hole placement; BC638TF for manual prototyping or repair.
MPSA92	Higher V_CEO (−300 V), lower I_C (−500 mA), lower h_FE (25–100), TO-92 package.	Better suited for high-voltage, low-current switching (e.g., CRT anode supplies); less optimal for 1 A load switching.	Choose MPSA92 only when >−100 V breakdown is required; otherwise BC638TF offers superior current handling.

Compared with BC638TA and MPSA92, BC638TF delivers optimal balance of 1 A current capability, −60 V rating, and wide h_FE range - making it preferred for general-purpose medium-power PNP switching where cost, availability, and proven reliability are critical.

Availability

BC638TF is available at Aetrix Electronics and suitable for relay drivers, linear regulator pass elements, half-bridge motor controls, and audio output stages requiring stable component supply and long-term manufacturability.

Supply support for BC638TF 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

onsemi (formerly ON Semiconductor) is a global semiconductor manufacturer specializing in energy-efficient power, analog, sensor, and connectivity solutions for automotive, industrial, cloud, and consumer markets.

The BC638TF belongs to onsemi's legacy general-purpose bipolar transistor family, engineered for robustness, consistency, and broad applicability in discrete power control and amplification circuits.

FAQ

What is the maximum continuous collector current rating for BC638TF?

The BC638TF has a maximum continuous collector current rating of −1 A at T_A = 25°C. This rating assumes adequate PCB copper area for heat dissipation; derating is required above 25°C ambient at 8 mW/°C. At I_C = −500 mA, the device maintains V_CE(sat) ≤ −0.5 V with appropriate base drive, confirming its suitability for medium-power switching applications.

Is BC638TF pin-compatible with BC637?

No - BC638TF is a PNP transistor while BC637 is an NPN device; they share identical TO-92-3 package pinout (Emitter-Collector-Base for BC638TF, Collector-Emitter-Base for BC637), but polarity reversal means direct substitution without circuit redesign is not possible. They are complementary in function, not pin-compatible.

Does BC638TF meet RoHS and lead-free requirements?

Yes, BC638TF is Pb-free, halogen-free/BFR-free, and fully RoHS compliant per onsemi's documentation. The device carries no hazardous substance exemptions and conforms to EU Directive 2011/65/EU and related global environmental standards without performance compromise.

What is the typical DC current gain (h_FE) of BC638TF at different operating points?

BC638TF exhibits current-dependent h_FE: minimum 25 at I_C = −5 mA, 40–160 at I_C = −150 mA, and 25 again at I_C = −500 mA (all at V_CE = −2 V). This profile reflects optimized mid-current gain and confirms design intent for switching and amplification across a broad load range.

Can BC638TF be used in audio amplifier output stages?

Yes, BC638TF is suitable for Class-A or Class-AB audio output stages due to its f_T = 100 MHz, low V_CE(sat), and stable h_FE behavior. It delivers clean signal reproduction up to 20 kHz when biased appropriately, and its TO-92 package allows easy heatsinking in low-power designs - confirmed in onsemi's typical performance curves.

BC638TF 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:: PNP

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

Voltage - Collector Emitter Breakdown (Max):: 60 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

BC638TF FAQ

1.How can I place an order for BC638TF through Aetrix?

Please submit a Request for Quotation (RFQ) for BC638TF 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 BC638TF reliable?

The price and inventory of BC638TF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BC638TF is usually 5 days.

3.What payment methods are accepted for BC638TF?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BC638TF transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BC638TF?

BC638TF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BC638TF 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 BC638TF?

For technical support, including BC638TF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BC638TF requirements.

6.How does Aetrix verify that BC638TF is sourced from the original manufacturer or authorized distributors?

All BC638TF 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 BC638TF meets industry standards.

7.What is the process for return or replacement of BC638TF?

All BC638TF units undergo pre-shipment inspection (PSI). If there is an issue with BC638TF, 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 BC638TF part is unused and in its original packaging.

Return procedure for BC638TF:

1.Submit a request within 90 days.

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

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