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

onsemi BD37725STU

Name: BD37725STU
Brand: onsemi
SKU: BD37725STU
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BD37725STU

Manufacturer:: onsemi

Category:: Single Bipolar Transistors

Package:: TO-225AA, TO-126-3

Datasheet:: BD37725STU.pdf

Description:: TRANS NPN 60V 2A TO-126-3

Quantity:: RFQ Add To RFQ list

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Product details

Overview

BD37725STU from Fairchild Semiconductor is an NPN epitaxial silicon transistor in TO-126 package, rated for 60 V V_CEO, 2 A continuous collector current, 25 W power dissipation at T_C = 25°C, and 150°C maximum junction temperature-used in medium-power linear amplification and switching applications such as audio output stages and relay drivers.

For engineers reviewing the BD37725STU datasheet, pinout, applications, or equivalent options, key selection criteria include V_CEO = 60 V, h_FE = 63–160 (at I_C = 0.15 A), V_CE(sat) = 1 V (I_C = 1 A, I_B = 0.1 A), t_OFF = 500 ns, and TO-126 thermal performance with case-mounted heatsinking.

Technical Context

This NPN bipolar junction transistor operates in active, saturation, and cutoff regions with defined safe operating area (SOA) limits up to 60 V and 2 A DC. Its h_FE classification (63–160 at I_C = 0.15 A) and low V_CE(sat) support efficient switching in medium-power loads, while its 500 ns turn-off time enables operation in audio-frequency switching circuits.

The device features a complementary pair relationship with BD378 and is designed for direct mounting to heatsinks via its metal tab (Pin 2, Collector). Thermal derating begins at T_C > 25°C, with full power limited to 25 W only at case temperature ≤25°C per the published derating curve.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	60 V - Maximum collector-emitter voltage before breakdown under open-base conditions; defines safe DC voltage swing in switching or amplifier output stage.
I_C (DC)	2 A - Continuous collector current rating; sets maximum steady-state load current without forced cooling.
P_C (T_C=25°C)	25 W - Maximum power dissipation at case temperature of 25°C; requires heatsink for sustained operation above ~1 W at elevated T_C.
h_FE (I_C=0.15 A)	63–160 - DC current gain range at moderate bias; determines base drive requirements for linear gain or saturated switch operation.
V_CE(sat)	1 V @ I_C=1 A, I_B=0.1 A - Saturation voltage defining conduction loss in switching mode; impacts efficiency and thermal rise in on-state.
t_OFF	500 ns - Turn-off delay under specified test conditions (V_CC=30 V, R_L=60 Ω); constrains maximum usable switching frequency in hard-switched applications.

Pinout & Package

BD37725STU uses the TO-126 package: molded plastic case with metal tab (Collector) for heatsink mounting, 3-pin through-hole configuration, and standardized lead spacing per JEDEC TO-126 outline.

Pin/Terminal	Circuit Role	Design Meaning
1	Emitter	Current exit path; connected to ground or low-side reference in common-emitter configurations.
2	Collector	Main current input path and thermal interface; metal tab is electrically connected to Collector and must be isolated from chassis unless circuit design permits.
3	Base	Control terminal for current amplification; requires current-limited drive (max I_B = 1 A) to avoid damage during transient overdrive.

Key Features

Feature	Design Value
Medium-power SOA	Defined safe operating area up to 60 V × 2 A with thermal derating; supports robust linear and switching operation without secondary breakdown.
Complementary pairing	Designed as NPN counterpart to BD378 (PNP), enabling push-pull output stages in audio amplifiers and motor drivers.
Low V_CE(sat)	1 V at I_C/I_B = 10; reduces conduction loss and self-heating in saturated switching applications.
TO-126 thermal interface	Metal tab (Collector) provides direct thermal path to heatsink; enables >20 W dissipation with modest heatsinking at T_C ≤ 70°C.

Applications

Audio Power Amplifier Output Stage	DC Motor Driver (H-Bridge Low-Side)
Use Scenario: Final output stage in Class AB audio amplifiers delivering up to 15 W into 8 Ω loads. IC Role / Device Role / Timing Role: NPN power transistor in common-emitter configuration, biased for linear operation with complementary PNP (BD378). Use Value: 60 V V_CEO and 2 A I_C support rail voltages up to ±30 V; h_FE consistency ensures predictable bias stability across production units.	Use Scenario: Low-side switch in half-bridge or H-bridge motor control for 12–24 V brushed DC motors. IC Role / Device Role / Timing Role: Saturated NPN switch controlling motor current flow to ground; driven by logic-level base driver. Use Value: 1 V V_CE(sat) minimizes I²R loss at 1–2 A load current; 500 ns t_OFF allows PWM frequencies up to ~200 kHz without excessive switching loss.
Relay Driver Circuit	Linear Voltage Regulator Pass Element
Use Scenario: Driving 12 V/500 mA electromagnetic relays from microcontroller GPIO pins. IC Role / Device Role / Timing Role: Switching transistor amplifying low-current logic signal to energize relay coil. Use Value: 2 A I_C rating provides 4× safety margin over typical relay coil current; TO-126 mechanical robustness supports industrial board-mount reliability.	Use Scenario: Series pass element in adjustable linear regulators supplying 1–2 A at up to 50 V input-to-output differential. IC Role / Device Role / Timing Role: Continuously biased NPN transistor dissipating excess power as heat to maintain regulated output voltage. Use Value: 25 W P_C at T_C = 25°C and defined SOA enable stable operation under worst-case dropout and load conditions.

Audio Power Amplifier Output Stage

DC Motor Driver (H-Bridge Low-Side)

Use Scenario: Final output stage in Class AB audio amplifiers delivering up to 15 W into 8 Ω loads.

IC Role / Device Role / Timing Role: NPN power transistor in common-emitter configuration, biased for linear operation with complementary PNP (BD378).

Use Value: 60 V V_CEO and 2 A I_C support rail voltages up to ±30 V; h_FE consistency ensures predictable bias stability across production units.

Use Scenario: Low-side switch in half-bridge or H-bridge motor control for 12–24 V brushed DC motors.

IC Role / Device Role / Timing Role: Saturated NPN switch controlling motor current flow to ground; driven by logic-level base driver.

Use Value: 1 V V_CE(sat) minimizes I²R loss at 1–2 A load current; 500 ns t_OFF allows PWM frequencies up to ~200 kHz without excessive switching loss.

Relay Driver Circuit

Linear Voltage Regulator Pass Element

Use Scenario: Driving 12 V/500 mA electromagnetic relays from microcontroller GPIO pins.

IC Role / Device Role / Timing Role: Switching transistor amplifying low-current logic signal to energize relay coil.

Use Value: 2 A I_C rating provides 4× safety margin over typical relay coil current; TO-126 mechanical robustness supports industrial board-mount reliability.

Use Scenario: Series pass element in adjustable linear regulators supplying 1–2 A at up to 50 V input-to-output differential.

IC Role / Device Role / Timing Role: Continuously biased NPN transistor dissipating excess power as heat to maintain regulated output voltage.

Use Value: 25 W P_C at T_C = 25°C and defined SOA enable stable operation under worst-case dropout and load conditions.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
MJD31C	V_CEO = 100 V, I_C = 3 A, TO-220 package, higher h_FE (20–150), no h_FE binning	Higher voltage headroom and current capacity; larger footprint and different thermal mounting	Preferred when >60 V rail or >2 A peak load is required; requires PCB layout change due to TO-220 vs. TO-126.
BD139	V_CEO = 80 V, I_C = 1.5 A, TO-126 package, h_FE = 40–250 (at I_C = 0.1 A), lower P_C = 12.5 W	Near-identical package and pinout; reduced power handling and narrower V_CEO margin	Suitable for lower-power replacements where 60 V and 25 W are not critical; verify SOA compliance in linear applications.

Compared with BD37725STU, MJD31C offers higher voltage/current ratings but requires TO-220 layout changes, while BD139 retains TO-126 compatibility but sacrifices 25% current capability and 50% power dissipation-making BD37725STU optimal for 60 V, 2 A, 25 W medium-power switching or linear use cases requiring proven SOA behavior.

Availability

BD37725STU is available at Aetrix Electronics and suitable for audio amplifier output stages, DC motor drivers, relay interface circuits, and linear regulator pass elements requiring stable component supply and long-term industrial availability.

Supply support for BD37725STU 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 discrete devices, analog ICs, and interface solutions before its acquisition by ON Semiconductor in 2016.

The BD37725STU belongs to Fairchild's BD375/377/379 family of medium-power NPN transistors, engineered for reliable linear amplification and switching in industrial and consumer audio systems where SOA integrity and thermal stability are critical.

FAQ

What is the maximum collector-emitter voltage rating for BD37725STU?

The BD37725STU has a maximum collector-emitter voltage (V_CEO) rating of 60 V at T_C = 25°C. This rating applies under open-base conditions and defines the upper limit of voltage the transistor can block in common-emitter configuration without breakdown. Exceeding this value risks avalanche failure, especially under transient conditions or elevated temperatures.

Does BD37725STU have a specified h_FE range, and at what test conditions?

Yes, BD37725STU has an h_FE classification range of 63–160, measured at V_CE = 2 V and I_C = 0.15 A. This range reflects factory binning for DC current gain consistency. At higher current (I_C = 1 A), h_FE drops to a minimum of 20, which is critical for designing base drive in saturated switching applications.

What is the thermal resistance and heatsinking requirement for BD37725STU?

BD37725STU uses a TO-126 package with the Collector connected to the metal tab, enabling direct heatsink mounting. While no explicit R_θJC is published, the datasheet specifies 25 W power dissipation only at T_C = 25°C, with linear derating above that temperature. A minimum heatsink surface area of ~15 cm² with thermal interface material is recommended for sustained 10 W operation at ambient ≤50°C.

Is BD37725STU pin-compatible with other transistors in the BD375/377/379 series?

Yes, BD37725STU shares identical TO-126 pinout (Emitter-Collector-Base) and mechanical dimensions with BD375 and BD379. However, electrical ratings differ: BD375 is rated for 45 V V_CEO, BD379 for 80 V. Substitution requires verification of voltage, current, and SOA requirements in the target circuit-BD37725STU is not a drop-in replacement without design review.

What is the typical turn-off time (t_OFF) for BD37725STU, and how does it affect switching performance?

The BD37725STU has a typical turn-off time (t_OFF) of 500 ns under test conditions of V_CC = 30 V, I_C = 0.5 A, R_L = 60 Ω, and base drive reversal (I_B1 = –I_B2 = 0.05 A). This value limits practical PWM switching frequency to ~200 kHz in hard-switched applications, as higher frequencies increase switching losses and require careful base drive optimization to minimize storage time.

BD37725STU Specifications

Product attributes: Attribute value

Manufacturer:: onsemi

Series:: -

Package/Case:: TO-225AA, TO-126-3

Packaging:: Tube

Product Status:: Obsolete

Transistor Type:: NPN

Current - Collector (Ic) (Max):: 2 A

Voltage - Collector Emitter Breakdown (Max):: 60 V

Vce Saturation (Max) @ Ib, Ic:: 1V @ 100mA, 1A

Current - Collector Cutoff (Max):: 2µA (ICBO)

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

Power - Max:: 25 W

Frequency - Transition:: -

Operating Temperature:: 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: TO-126-3

BD37725STU FAQ

1.How can I place an order for BD37725STU through Aetrix?

Please submit a Request for Quotation (RFQ) for BD37725STU 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 BD37725STU reliable?

The price and inventory of BD37725STU are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BD37725STU is usually 5 days.

3.What payment methods are accepted for BD37725STU?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BD37725STU transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BD37725STU?

BD37725STU orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BD37725STU 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 BD37725STU?

For technical support, including BD37725STU datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BD37725STU requirements.

6.How does Aetrix verify that BD37725STU is sourced from the original manufacturer or authorized distributors?

All BD37725STU 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 BD37725STU meets industry standards.

7.What is the process for return or replacement of BD37725STU?

All BD37725STU units undergo pre-shipment inspection (PSI). If there is an issue with BD37725STU, 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 BD37725STU part is unused and in its original packaging.

Return procedure for BD37725STU:

1.Submit a request within 90 days.

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

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