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

onsemi BD242BG

Name: BD242BG
Brand: onsemi
SKU: BD242BG
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BD242BG

Manufacturer:: onsemi

Category:: Single Bipolar Transistors

Package:: TO-220-3

Datasheet:: BD242BG.pdf

Description:: TRANS PNP 80V 3A TO-220

Quantity:: RFQ Add To RFQ list

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Product details

Overview

BD242BG from ON Semiconductor is an NPN epitaxial silicon power transistor in TO-220 package, rated for 45 V V_CEO, 3 A continuous collector current, and 40 W collector dissipation at T_C = 25°C. It serves as a medium-power linear amplifier and switching device in DC motor drives, power supplies, and relay drivers.

For engineers reviewing the BD242BG datasheet, pinout, applications, or equivalent options, key selection criteria include V_CEO rating, h_FE consistency at 1–3 A, V_CE(sat) under 1.2 V at I_C = 3 A / I_B = 0.6 A, thermal performance in TO-220, and complementary pairing with BD241G.

Technical Context

The BD242BG operates as a general-purpose NPN bipolar junction transistor optimized for linear and switching applications up to 45 V and 3 A. Its DC current gain (h_FE) is specified at 25 minimum at I_C = 1 A and 10 minimum at I_C = 3 A, with V_CE(sat) ≤ 1.2 V under forced beta of 5.

Junction temperature is rated to 150°C, and storage temperature spans −65°C to +150°C. The device features V_EBO = 5 V, I_C pulse capability of 5 A (PW = 350 µs, duty ≤ 2%), and low leakage: I_CEO ≤ 0.3 mA at V_CE = 30 V.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	45 V - Maximum safe collector-emitter voltage before breakdown in open-base configuration
I_C (DC)	3 A - Continuous collector current limit requiring heatsinking above ambient ~50°C
P_C (T_C=25°C)	40 W - Total power dissipation achievable only with case temperature held at 25°C
h_FE	25 min @ I_C=1A - Ensures stable biasing in Class-A amplifiers and predictable switching drive requirements
V_CE(sat)	≤1.2 V @ I_C=3A/I_B=0.6A - Limits conduction loss to <3.6 W in saturated switch operation
T_J	150°C - Maximum allowable junction temperature; derating required above 25°C case temperature

Pinout & Package

BD242BG uses the standard TO-220 package with 3 leads: Base (lead 1), Collector (lead 2), Emitter (lead 3). Mounting tab is electrically connected to the collector.

Pin/Terminal	Circuit Role	Design Meaning
1 (Base)	Control input terminal	Receives base current to enable conduction; requires current-limiting resistor in most driver circuits
2 (Collector)	High-side output terminal	Connected to load or supply rail; tab is collector-requires isolation when mounted to heatsink
3 (Emitter)	Low-side return terminal	Typically tied to ground or negative rail; forms common reference for base drive and load current return

Key Features

Feature	Design Value
Complementary Pairing	Designed as direct complement to BD241G (NPN/PNP pair) for push-pull and H-bridge output stages
Medium-Power Switching	Rated for reliable 3 A DC switching with V_CE(sat) ≤ 1.2 V-reduces heat generation vs. lower-gain alternatives
TO-220 Thermal Interface	Standardized mechanical footprint enables use with off-the-shelf heatsinks and mounting hardware
Industrial Temperature Range	−65°C to +150°C operating/storage range supports deployment in automotive engine bays and industrial controls

Applications

DC Motor Control	Linear Power Supply Regulator
Use Scenario: Driving 12 V/2 A brushed DC motors in industrial actuators and HVAC dampers. IC Role / Device Role / Timing Role: NPN power switch controlling motor direction and on/off state via base drive from microcontroller GPIO. Use Value: V_CE(sat) ≤ 1.2 V minimizes I²R loss at 3 A, enabling >92% efficiency in PWM-driven half-bridge configurations.	Use Scenario: Pass transistor in adjustable 0–30 V, 3 A linear bench power supply. IC Role / Device Role / Timing Role: Series pass element regulated by op-amp feedback loop; dissipates excess voltage as heat. Use Value: 40 W P_C rating allows safe operation at 15 V dropout × 2.5 A = 37.5 W without forced cooling.
Relay Driver Circuit	Switch-Mode Power Supply Auxiliary
Use Scenario: Driving 24 V/500 mA electromagnetic relays in PLC I/O modules. IC Role / Device Role / Timing Role: Saturated switch interfacing between logic-level controller and inductive relay coil. Use Value: h_FE ≥ 25 at 1 A ensures full saturation with ≤40 mA base drive-compatible with standard 5 V MCU outputs.	Use Scenario: Secondary-side synchronous rectifier or auxiliary bias supply switch in flyback converters. IC Role / Device Role / Timing Role: Low-duty-cycle switching element handling peak currents during transient load steps. Use Value: 5 A pulsed rating (350 µs, ≤2% duty) supports surge handling during startup and overload recovery.

DC Motor Control

Linear Power Supply Regulator

Use Scenario: Driving 12 V/2 A brushed DC motors in industrial actuators and HVAC dampers.

IC Role / Device Role / Timing Role: NPN power switch controlling motor direction and on/off state via base drive from microcontroller GPIO.

Use Value: V_CE(sat) ≤ 1.2 V minimizes I²R loss at 3 A, enabling >92% efficiency in PWM-driven half-bridge configurations.

Use Scenario: Pass transistor in adjustable 0–30 V, 3 A linear bench power supply.

IC Role / Device Role / Timing Role: Series pass element regulated by op-amp feedback loop; dissipates excess voltage as heat.

Use Value: 40 W P_C rating allows safe operation at 15 V dropout × 2.5 A = 37.5 W without forced cooling.

Relay Driver Circuit

Switch-Mode Power Supply Auxiliary

Use Scenario: Driving 24 V/500 mA electromagnetic relays in PLC I/O modules.

IC Role / Device Role / Timing Role: Saturated switch interfacing between logic-level controller and inductive relay coil.

Use Value: h_FE ≥ 25 at 1 A ensures full saturation with ≤40 mA base drive-compatible with standard 5 V MCU outputs.

Use Scenario: Secondary-side synchronous rectifier or auxiliary bias supply switch in flyback converters.

IC Role / Device Role / Timing Role: Low-duty-cycle switching element handling peak currents during transient load steps.

Use Value: 5 A pulsed rating (350 µs, ≤2% duty) supports surge handling during startup and overload recovery.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
MJD242G	Same V_CEO (45 V), but in DPAK package; lower P_C (25 W); h_FE min 25 @ I_C=1A	Suitable for surface-mount designs with moderate power density; not drop-in for through-hole TO-220 layouts	Select MJD242G only if board space constraints require SMT and thermal design accommodates 25 W limit.
BD242C	Higher V_CEO (100 V), same TO-220 package and pinout; otherwise identical electrical specs at 3 A	Preferred where system transients exceed 45 V or design margin requires higher breakdown rating	BD242C offers direct PCB compatibility and enhanced voltage safety margin without layout change.

Compared with BD242BG, MJD242G trades package form factor and thermal capacity for SMT integration, while BD242C retains identical mechanical fit but extends voltage robustness-making it a true upgrade path for systems facing line surges or inductive kickback.

Availability

BD242BG is available at Aetrix Electronics and suitable for DC motor control, linear power supply regulation, and relay driver applications requiring stable component supply, long-term industrial availability, and consistent parametric performance across production batches.

Supply support for BD242BG 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 manufacturer specializing in energy-efficient power, analog, sensor, and connectivity solutions for automotive, industrial, cloud, and consumer markets.

The BD242BG belongs to ON Semiconductor's legacy Fairchild power transistor product line, designed specifically for cost-sensitive, medium-power linear and switching applications where reliability, thermal stability, and complementary pairing are essential.

FAQ

What is the maximum collector-emitter voltage rating for BD242BG?

The BD242BG has a maximum collector-emitter voltage (V_CEO) rating of 45 V at T_C = 25°C. This rating applies under open-base conditions and defines the upper limit for safe DC or peak repetitive voltage across the collector and emitter terminals. Exceeding this value risks avalanche breakdown and permanent device failure. Derating is required at elevated case temperatures per the datasheet's thermal curves.

Does BD242BG have a built-in base-emitter resistor?

No, BD242BG is a standard discrete NPN bipolar junction transistor without any integrated base-emitter resistors. It requires external base current limiting-typically via a series resistor driven by a microcontroller or logic gate-to ensure proper biasing and prevent thermal runaway. This distinguishes it from digital transistors (e.g., NSD series) that integrate resistors internally.

Is BD242BG pin-compatible with BD242C?

Yes, BD242BG and BD242C share identical TO-220 package dimensions, pinout (Base–Collector–Emitter), and mechanical mounting interface. However, BD242C is rated for 100 V V_CEO, whereas BD242BG is rated for 45 V. Electrical substitution is possible only if the application's voltage stress remains within 45 V; otherwise, BD242C provides enhanced margin without layout changes.

What is the typical DC current gain (h_FE) of BD242BG at 3 A collector current?

The BD242BG specifies a minimum h_FE of 10 at V_CE = 4 V and I_C = 3 A. Typical values observed in production lots range from 15 to 22 under those conditions. Designers should size base drive circuitry to deliver ≥300 mA (I_B = I_C/10) to guarantee saturation across process and temperature extremes.

Can BD242BG be used in parallel for higher current handling?

BD242BG is not recommended for direct paralleling without individual emitter resistors due to positive thermal feedback and h_FE variation across units. If higher current is needed, use a single higher-rated device (e.g., BD243C or TIP31C), or implement active current sharing with matched base drive and emitter degeneration resistors-each sized to balance static current to within ±10% at full load.

BD242BG Specifications

Product attributes: Attribute value

Manufacturer:: onsemi

Series:: -

Package/Case:: TO-220-3

Packaging:: Tube

Product Status:: Obsolete

Transistor Type:: PNP

Current - Collector (Ic) (Max):: 3 A

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

Vce Saturation (Max) @ Ib, Ic:: 1.2V @ 600mA, 3A

Current - Collector Cutoff (Max):: 300µA

DC Current Gain (hFE) (Min) @ Ic, Vce:: 25 @ 1A, 4V

Power - Max:: 40 W

Frequency - Transition:: 3MHz

Operating Temperature:: -65°C ~ 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: TO-220

BD242BG FAQ

1.How can I place an order for BD242BG through Aetrix?

Please submit a Request for Quotation (RFQ) for BD242BG 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 BD242BG reliable?

The price and inventory of BD242BG are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BD242BG is usually 5 days.

3.What payment methods are accepted for BD242BG?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BD242BG transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BD242BG?

BD242BG orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BD242BG 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 BD242BG?

For technical support, including BD242BG datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BD242BG requirements.

6.How does Aetrix verify that BD242BG is sourced from the original manufacturer or authorized distributors?

All BD242BG 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 BD242BG meets industry standards.

7.What is the process for return or replacement of BD242BG?

All BD242BG units undergo pre-shipment inspection (PSI). If there is an issue with BD242BG, 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 BD242BG part is unused and in its original packaging.

Return procedure for BD242BG:

1.Submit a request within 90 days.

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

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