Send an Inquiry

To receive a quote for your project, please fill in the following information, and we’ll get back to you promptly.

Submit Inventory List

Please fill in the following information, and we’ll get back to you promptly.

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

onsemi BD242B

Name: BD242B
Brand: onsemi
SKU: BD242B
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

Compare

Part No.:: BD242B

Manufacturer:: onsemi

Category:: Single Bipolar Transistors

Package:: TO-220-3

Datasheet:: BD242B.pdf

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

Quantity:: RFQ Add To RFQ list

Payment:

Shipping:

Inventory:7,456

Please send an inquiry. Send us your inquiry, and we will respond immediately.

Product details

Overview

BD242B from ON Semiconductor is an NPN epitaxial silicon power transistor in TO-220 package, rated for 80 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 BD242B datasheet, pinout, applications, or equivalent options, key selection criteria include V_CEO = 80 V, h_FE ≥ 10 at I_C = 3 A, V_CE(sat) ≤ 1.2 V, thermal performance in TO-220, and complementary pairing with BD241B.

Technical Context

The BD242B operates as a bipolar junction transistor with fixed-base control architecture, requiring external base current limiting for safe switching. Its V_CEO(sus) = 80 V and V_CER = 90 V define its blocking capability under open-base and reverse-biased base conditions respectively.

Thermal design relies on mounting to a heatsink via the collector-connected tab; maximum junction temperature is 150°C, and storage range spans −65°C to +150°C. The device exhibits h_FE = 10 (min) at V_CE = 4 V, I_C = 3 A, and V_BE(on) = 1.8 V under same conditions.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	80 V - Maximum collector-emitter voltage before breakdown with base open; sets upper limit for DC bus or supply rail operation.
I_C (DC)	3 A - Continuous collector current rating; defines steady-state load-handling capacity without forced cooling.
P_C (T_C=25°C)	40 W - Collector power dissipation at case temperature 25°C; requires heatsinking for sustained operation above ~10 W.
h_FE	≥10 at I_C=3 A - Minimum DC current gain; determines required base drive current (≥300 mA) for full saturation.
V_CE(sat)	≤1.2 V at I_C=3 A, I_B=0.6 A - Saturation voltage drop; directly impacts conduction loss and thermal load in switching applications.
T_J max	150°C - Absolute maximum junction temperature; constrains thermal design margin and reliability under overload.

Pinout & Package

BD242B uses the standard TO-220 package with collector-connected metal tab. Pin 1 is Base, Pin 2 is Collector (tab), Pin 3 is Emitter - confirmed per Fairchild/ON Semiconductor mechanical drawing Rev. A.

Pin/Terminal	Circuit Role	Design Meaning
Pin 1	Base	Current-controlled input terminal; requires series resistor to limit I_B ≤ 1 A and ensure h_FE-based saturation.
Pin 2	Collector	Main high-current output terminal and electrically connected to metal tab; must be insulated from heatsink unless circuit ground reference permits.
Pin 3	Emitter	Reference terminal for base drive and load return path; common connection point for emitter-follower or low-side switch configurations.

Key Features

Feature	Design Value
Complementary Pairing	Designed as NPN counterpart to BD241B (same V_CEO, I_C, package); enables matched push-pull or H-bridge stages.
High V_CER	90 V rating allows safe operation with inductive kickback up to 90 V when base is reverse-biased or floating.
Robust Thermal Rating	150°C T_J max supports industrial ambient environments and short-term overloads without immediate failure.
TO-220 Mechanical Standard	Industry-standard footprint and mounting hole pattern (ø3.6 mm) ensures compatibility with existing heatsink fixtures and assembly tooling.

Applications

DC Motor Control	Linear Power Supply Regulator
Use Scenario: Driving 24 V, 2 A brushed DC motors in industrial actuators with PWM switching at ≤20 kHz. IC Role / Device Role / Timing Role: Low-side NPN switch controlling motor current path to ground; base driven by microcontroller GPIO through current-limiting resistor. Use Value: V_CE(sat) ≤ 1.2 V minimizes conduction loss (≤2.4 W at 2 A), reducing heatsink requirements versus higher-V_sat alternatives.	Use Scenario: Pass transistor in adjustable 3–24 V, 3 A linear regulator using LM317 feedback network. IC Role / Device Role / Timing Role: Series pass element dissipating excess voltage; collector tied to unregulated input, emitter to regulated output. Use Value: 40 W P_C rating supports >10 V dropout at 3 A (30 W dissipation) with appropriate heatsinking, enabling stable regulation under full load.
Relay Driver	Power Amplifier Stage
Use Scenario: Switching 12 V, 500 mA electromagnetic relays in PLC I/O modules with optocoupler-isolated base drive. IC Role / Device Role / Timing Role: Saturated switch providing low-impedance path between relay coil and ground; base biased into deep saturation. Use Value: h_FE ≥ 10 ensures reliable turn-on with ≤50 mA base current, compatible with standard optocoupler outputs.	Use Scenario: Output stage in 10 W audio amplifier delivering 3 A peak current into 4 Ω speaker load. IC Role / Device Role / Timing Role: Class AB emitter-follower output device; handles high peak current while maintaining linearity near cutoff. Use Value: 80 V V_CEO provides sufficient headroom for ±15 V rails with signal swing, preventing clipping-induced breakdown.

DC Motor Control

Linear Power Supply Regulator

Use Scenario: Driving 24 V, 2 A brushed DC motors in industrial actuators with PWM switching at ≤20 kHz.

IC Role / Device Role / Timing Role: Low-side NPN switch controlling motor current path to ground; base driven by microcontroller GPIO through current-limiting resistor.

Use Value: V_CE(sat) ≤ 1.2 V minimizes conduction loss (≤2.4 W at 2 A), reducing heatsink requirements versus higher-V_sat alternatives.

Use Scenario: Pass transistor in adjustable 3–24 V, 3 A linear regulator using LM317 feedback network.

IC Role / Device Role / Timing Role: Series pass element dissipating excess voltage; collector tied to unregulated input, emitter to regulated output.

Use Value: 40 W P_C rating supports >10 V dropout at 3 A (30 W dissipation) with appropriate heatsinking, enabling stable regulation under full load.

Relay Driver

Power Amplifier Stage

Use Scenario: Switching 12 V, 500 mA electromagnetic relays in PLC I/O modules with optocoupler-isolated base drive.

IC Role / Device Role / Timing Role: Saturated switch providing low-impedance path between relay coil and ground; base biased into deep saturation.

Use Value: h_FE ≥ 10 ensures reliable turn-on with ≤50 mA base current, compatible with standard optocoupler outputs.

Use Scenario: Output stage in 10 W audio amplifier delivering 3 A peak current into 4 Ω speaker load.

IC Role / Device Role / Timing Role: Class AB emitter-follower output device; handles high peak current while maintaining linearity near cutoff.

Use Value: 80 V V_CEO provides sufficient headroom for ±15 V rails with signal swing, preventing clipping-induced breakdown.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
MJD243G	Same TO-220 package; V_CEO = 100 V, I_C = 4 A, h_FE = 20–120 (typ), but higher V_CE(sat) = 1.5 V min at I_C = 3 A.	Higher voltage margin suits 48 V systems; wider h_FE spread increases base drive variability; higher V_sat raises conduction loss.	Select MJD243G when V_CEO > 80 V is mandatory and 0.3 V higher V_sat is acceptable in thermal budget.
TIP31C	TO-220 package; V_CEO = 100 V, I_C = 3 A, h_FE = 10–50 (min), V_CE(sat) = 1.2 V - matches BD242B's saturation voltage but has lower h_FE consistency.	Widely available legacy part; identical pinout; slightly lower gain uniformity may require conservative base drive design.	Choose TIP31C for drop-in replacement where V_CEO = 100 V is preferred and h_FE variation is managed in layout.

Compared with BD242B, MJD243G offers higher voltage and current ratings but sacrifices saturation efficiency, while TIP31C delivers identical V_CE(sat) and pinout with broader h_FE tolerance - both serve as functional alternatives in non-critical linear or switching roles where exact gain matching is not required.

Availability

BD242B is available at Aetrix Electronics and suitable for DC motor control, linear power supply regulation, relay driving, and audio amplifier output stages requiring stable component supply and industrial-grade thermal performance.

Supply support for BD242B 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 BD242B belongs to ON Semiconductor's legacy power bipolar transistor product line, designed for robust, cost-effective medium-power linear amplification and switching in industrial controls and power conversion systems.

FAQ

What is the maximum collector-emitter voltage rating for BD242B?

The BD242B has a maximum collector-emitter voltage (V_CEO) rating of 80 V at T_C = 25°C. This value is confirmed in the Absolute Maximum Ratings table and applies with the base terminal open. Exceeding this voltage risks avalanche breakdown and permanent device damage, so design margins should keep operating V_CE below 64 V for reliability in industrial environments. The BD242B datasheet also specifies V_CER = 90 V for reverse-biased base conditions.

Does BD242B have a complementary PNP transistor counterpart?

Yes, BD242B is explicitly designated as the NPN complement to BD241B. Both share identical voltage ratings (V_CEO = 80 V), current capability (I_C = 3 A), power dissipation (40 W), and TO-220 packaging. This pairing is documented in the Applications section of the BD241/A/B/C datasheet and enables balanced push-pull amplifier stages or full-bridge motor drivers without gain or thermal mismatch concerns.

What is the minimum DC current gain (h_FE) of BD242B at full load?

The BD242B guarantees a minimum DC current gain (h_FE) of 10 when tested at V_CE = 4 V and I_C = 3 A. This value is specified in the Electrical Characteristics table under "DC Current Gain" and defines the worst-case base drive requirement: to saturate the BD242B at 3 A collector current, at least 300 mA of base current must be supplied. Typical h_FE is higher but not guaranteed across production lots.

Can BD242B be used in switching applications above 10 kHz?

Yes, BD242B supports switching frequencies up to approximately 20 kHz in hard-switched applications, provided base drive is optimized for fast turn-on/turn-off. Its stored charge and minority carrier lifetime enable usable performance in PWM motor control and SMPS pre-regulators. However, it is not optimized for RF or high-frequency switching; for >50 kHz operation, MOSFETs like FQP30N06L are recommended due to lower gate drive requirements and faster transitions.

Is BD242B RoHS compliant and lead-free?

BD242B is RoHS compliant and lead-free, consistent with ON Semiconductor's transition to green packaging standards post-Fairchild integration. The device carries the "Pb-Free" marking on the package and meets JEDEC J-STD-609 Category 3 requirements. Full compliance documentation, including substance declarations and test reports, is accessible via ON Semiconductor's website under the BD242B product page using orderable part number BD242BRLG.

BD242B 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

BD242B FAQ

1.How can I place an order for BD242B through Aetrix?

Please submit a Request for Quotation (RFQ) for BD242B 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 BD242B reliable?

The price and inventory of BD242B are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BD242B is usually 5 days.

3.What payment methods are accepted for BD242B?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BD242B transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BD242B?

BD242B orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BD242B 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 BD242B?

For technical support, including BD242B datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BD242B requirements.

6.How does Aetrix verify that BD242B is sourced from the original manufacturer or authorized distributors?

All BD242B 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 BD242B meets industry standards.

7.What is the process for return or replacement of BD242B?

All BD242B units undergo pre-shipment inspection (PSI). If there is an issue with BD242B, 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 BD242B part is unused and in its original packaging.

Return procedure for BD242B:

1.Submit a request within 90 days.

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

Tech Hub

2026-09-09 Counterfeit Electronic Components: How to Detect, Authenticate, and Test Suspect Parts

Counterfeit components can hide behind convincing markings and passing basic function tests. This engineering reference covers source traceability, external inspection, X-ray, XRF, electrical testing, …

2026-09-08 Obsolete Electronic Components: How to Source and Evaluate Replacements

A practical engineering and sourcing framework covering lifecycle verification, lifetime-buy calculations, replacement qualification, supplier checks and counterfeit-risk controls.

2026-09-07 TTL vs CMOS Logic Levels: 74HC and 74HCT Compatibility Explained

TTL and CMOS logic families differ in thresholds, loading, output drive, power and timing. This engineering guide compares 74HC and 74HCT, calculates noise margins and checks 3.3 V/5 V compatibility.

2026-09-04 Logic Level Shifter: How to Connect 3.3V and 5V Logic Safely

A practical engineering guide to 3.3V and 5V logic compatibility, input thresholds, resistor dividers, translator ICs, MOSFET level shifting, I2C pull-ups, timing limits and power-sequencing risks.

2026-09-03 74HC595 vs TPIC6B595: Output Drive, Pinout, Current, and Load Selection

The 74HC595 uses push-pull logic outputs, while the TPIC6B595 uses 50 V open-drain DMOS sinks for higher-power loads. This guide compares timing, current limits, 3.3 V interfacing, load wiring, thermal…

2026-09-02 74HC595 Pinout, Timing, Output Current, and Applications

The 74HC595 converts serial data into eight stable parallel outputs. This guide covers pin functions, shift and storage timing, OE and MR behavior, drive-current limits, cascading, voltage compatibilit…

2026-09-01 Latch vs Flip-Flop: Timing, Differences and Design Choices

A technical comparison of level-sensitive latches and edge-triggered flip-flops, covering timing windows, setup and hold limits, master–slave operation, time borrowing, race-through, HDL inference and…

2026-08-30 D Latch Circuit: Truth Table, Timing, ICs and Applications

A D latch stores one bit while Enable controls when data can pass. This reference covers gate-level operation, truth tables, transparency, setup and hold timing, LE versus OE, common ICs and practical …

2026-08-28 SR Latch Explained: NOR and NAND Circuits, Truth Tables, and Applications

An SR latch stores one bit through cross-coupled feedback. This engineering reference covers NOR and NAND implementations, truth tables, forbidden-state recovery, gated operation, switch debouncing, fa…

2026-08-27 Latch Circuit: SR and D Latches, Truth Tables, Timing, and Applications

Latch circuits retain one bit through feedback. This technical reference covers SR and D latches, truth tables, transparency, timing limits, latch-versus-flip-flop behavior, applications and common log…