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 MPSA42RL1

Name: MPSA42RL1
Brand: onsemi
SKU: MPSA42RL1
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

Compare

Part No.:: MPSA42RL1

Manufacturer:: onsemi

Category:: Single Bipolar Transistors

Package:: TO-226-3, TO-92-3 Long Body, Formed Leads

Datasheet:: MPSA42RL1.pdf

Description:: TRANS NPN 300V 0.5A TO92

Quantity:: RFQ Add To RFQ list

Payment:

Shipping:

Inventory:8,556

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

Product details

Overview

MPSA42RL1 from onsemi is an NPN silicon high-voltage general-purpose transistor in TO-92 package, rated for 300 V_CEO, 500 mA continuous collector current, and 625 mW power dissipation at T_A = 25°C. It serves as a switching or linear amplifier in high-voltage interface circuits, such as telephone line interface cards and flyback converter base drive stages.

For engineers reviewing the MPSA42RL1 datasheet, pinout, applications, or equivalent options, key selection criteria include V_CEO = 300 V, h_FE ≥ 25 at I_C = 1.0 mA, V_CE(sat) ≤ 0.5 V at I_C/I_B = 10, C_cb = 3.0 pF, and TO-92 mechanical compatibility with legacy through-hole layouts.

Technical Context

The MPSA42RL1 operates as a discrete NPN bipolar junction transistor optimized for high-voltage switching up to 300 V with low saturation voltage and moderate gain bandwidth (f_T = 50 MHz). Its breakdown ratings-V_(BR)CEO = 300 V, V_(BR)CBO = 300 V, and V_(BR)EBO = 6.0 V-define safe operating limits under open-base and open-emitter conditions.

Thermal design relies on R_JA = 200°C/mW (ambient) and R_JC = 83.3°C/mW (case), supporting operation from −55°C to +150°C junction temperature. Derating begins above 25°C at 5.0 mW/°C for ambient and 12 mW/°C for case mounting.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	300 V - Maximum collector-emitter voltage before avalanche breakdown; enables use in 240 VAC-derived supply rails and telecom line interfaces.
I_C (continuous)	500 mA - Continuous collector current rating; supports medium-power switching loads like relay coils and LED strings.
h_FE	25–40 - DC current gain range at I_C = 1–30 mA; sufficient for simple current amplification without complex bias compensation.
V_CE(sat)	≤ 0.5 V at I_C = 20 mA, I_B = 2 mA - Low saturation voltage minimizes conduction loss in switching applications.
f_T	50 MHz - Transition frequency defines usable small-signal bandwidth; suitable for audio and low-MHz switching control signals.
C_cb	3.0 pF at V_CB = 20 V - Collector-base capacitance impacts high-frequency gain roll-off and switching speed in common-emitter configurations.

Pinout & Package

Package: TO-92 (Case 29−11), through-hole, 3-lead plastic package with standard lead spacing and mechanical dimensions per ON Semiconductor specification.

Pin/Terminal	Circuit Role	Design Meaning
1 (Emitter)	Current exit path for majority carriers	Connected to ground or low-side reference; polarity-sensitive for proper biasing and current flow direction.
2 (Collector)	Current entry path for majority carriers	Connected to high-voltage rail or load; withstands up to 300 V when base is open or reverse-biased.
3 (Base)	Control terminal for minority carrier injection	Receives current-limited drive signal; requires external resistor to limit I_B and ensure reliable turn-on/turn-off.

Key Features

Feature	Design Value
High-voltage capability	V_CEO = 300 V enables direct interface with off-line AC-derived supplies and telecom line voltages without external voltage division.
Low saturation voltage	V_CE(sat) ≤ 0.5 V reduces power loss and self-heating during active conduction, improving thermal margin in compact layouts.
Stable gain over temperature	h_FE maintains functional range across −55°C to +150°C, supporting industrial and automotive under-hood environments.
Pb-free packaging option	MPSA42RL1G variant available; RL1 suffix denotes tape-and-reel delivery (2000 units), enabling automated SMT-compatible through-hole placement.

Applications

Telephone Line Interface	Flyback Converter Base Drive
Use Scenario: Isolating and driving ring generator circuits in analog telephony equipment handling 90 V RMS ringing signals. IC Role / Device Role / Timing Role: High-voltage NPN switch controlling current into transformer primary winding during ringing pulse generation. Use Value: Withstands peak line transients up to 300 V while maintaining low V_CE(sat) to minimize heat in space-constrained line card designs.	Use Scenario: Driving gate/base of main power switch in low-cost isolated flyback converters for AC/DC adapters. IC Role / Device Role / Timing Role: Discrete BJT used in optocoupler feedback loop or auxiliary supply regulation circuitry. Use Value: Provides robust 300 V blocking capability and predictable h_FE for stable closed-loop response without requiring high-speed MOSFET drivers.
Industrial Sensor Signal Conditioning	Legacy Relay Driver Stage
Use Scenario: Amplifying low-level output from high-impedance sensors in PLC input modules exposed to 24–48 VDC field wiring. IC Role / Device Role / Timing Role: Linear amplifier stage converting sensor voltage to current-driven output compatible with opto-isolator inputs. Use Value: Maintains usable h_FE and low noise at I_C < 10 mA, enabling accurate low-current signal translation without op-amp complexity.	Use Scenario: Direct-driving electromagnetic relays rated for 24–125 VDC coils in building automation panels and HVAC controllers. IC Role / Device Role / Timing Role: General-purpose switching transistor interfacing microcontroller GPIO to relay coil with flyback diode protection. Use Value: Delivers 500 mA I_C with minimal board area and cost, avoiding need for dedicated driver ICs in low-volume industrial assemblies.

Telephone Line Interface

Flyback Converter Base Drive

Use Scenario: Isolating and driving ring generator circuits in analog telephony equipment handling 90 V RMS ringing signals.

IC Role / Device Role / Timing Role: High-voltage NPN switch controlling current into transformer primary winding during ringing pulse generation.

Use Value: Withstands peak line transients up to 300 V while maintaining low V_CE(sat) to minimize heat in space-constrained line card designs.

Use Scenario: Driving gate/base of main power switch in low-cost isolated flyback converters for AC/DC adapters.

IC Role / Device Role / Timing Role: Discrete BJT used in optocoupler feedback loop or auxiliary supply regulation circuitry.

Use Value: Provides robust 300 V blocking capability and predictable h_FE for stable closed-loop response without requiring high-speed MOSFET drivers.

Industrial Sensor Signal Conditioning

Legacy Relay Driver Stage

Use Scenario: Amplifying low-level output from high-impedance sensors in PLC input modules exposed to 24–48 VDC field wiring.

IC Role / Device Role / Timing Role: Linear amplifier stage converting sensor voltage to current-driven output compatible with opto-isolator inputs.

Use Value: Maintains usable h_FE and low noise at I_C < 10 mA, enabling accurate low-current signal translation without op-amp complexity.

Use Scenario: Direct-driving electromagnetic relays rated for 24–125 VDC coils in building automation panels and HVAC controllers.

IC Role / Device Role / Timing Role: General-purpose switching transistor interfacing microcontroller GPIO to relay coil with flyback diode protection.

Use Value: Delivers 500 mA I_C with minimal board area and cost, avoiding need for dedicated driver ICs in low-volume industrial assemblies.

Equivalent & Alternatives

The following parts are listed as comparable options for similar high-voltage NPN transistor applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
MPSA43	V_CEO = 200 V (vs. 300 V); otherwise identical pinout, package, and gain specs.	Not suitable where >200 V blocking is required; acceptable in lower-voltage industrial controls and relay drivers.	Select MPSA43 only if system maximum V_CE remains below 200 V; verify transient margin against surge events.
BC639	V_CEO = 60 V, higher h_FE (min 40), same TO-92 package and pinout (E-C-B).	Limited to sub-60 V applications; unsuitable for telecom or off-line derived supplies but preferred for low-voltage linear amplification.	Choose BC639 for cost-sensitive 5–24 V systems needing higher gain and lower V_CE(sat); avoid where >60 V stress occurs.

Compared with MPSA42RL1, MPSA43 offers reduced voltage rating but identical form factor and drive requirements, while BC639 trades voltage headroom for improved gain and lower saturation-making each viable only within its validated voltage envelope and thermal constraints.

Availability

MPSA42RL1 is available at Aetrix Electronics and suitable for telephone line interface cards, flyback converter auxiliary drives, and industrial relay control circuits requiring stable component supply and long-term obsolescence management.

Supply support for MPSA42RL1 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, sensing, and connectivity solutions for automotive, industrial, cloud, and consumer markets.

The MPSA42RL1 belongs to onsemi's Preferred Devices family of high-reliability, high-voltage discrete transistors designed for legacy-compatible, cost-sensitive industrial and telecom infrastructure applications.

FAQ

What is the maximum collector-emitter voltage rating for MPSA42RL1?

The MPSA42RL1 has a maximum collector-emitter voltage rating (V_CEO) of 300 Vdc, verified under test condition I_C = 1.0 mA with base open. This rating allows safe operation in circuits with peak voltages up to 300 V, including telecom line interfaces and off-line power supply auxiliary windings. Exceeding this voltage risks avalanche breakdown and permanent device failure.

Is MPSA42RL1 pin-compatible with MPSA43?

Yes, MPSA42RL1 and MPSA43 share identical TO-92 package dimensions and pinout (Emitter–Collector–Base, Style 14). However, MPSA43 has a lower V_CEO rating of 200 V versus 300 V for MPSA42RL1. Substitution is electrically valid only if the application's maximum V_CE remains below 200 V; no PCB changes are needed, but voltage margin must be re-verified.

What does the 'RL1' suffix mean in MPSA42RL1?

The 'RL1' suffix in MPSA42RL1 indicates tape-and-reel packaging with 2000 units per reel, optimized for automated through-hole insertion equipment. It is mechanically and electrically identical to the bulk-packaged MPSA42 but differs in logistics format-no performance or reliability differences exist between RL1 and non-RL1 variants of the same base part number.

Can MPSA42RL1 be used in linear amplifier configurations?

Yes, MPSA42RL1 supports linear operation with verified h_FE of 25–40 at I_C = 1–30 mA and V_CE = 10 V. Its f_T = 50 MHz and low C_cb = 3.0 pF enable stable audio-frequency amplification, though thermal derating must be applied above 25°C ambient to maintain safe junction temperature in continuous bias.

Does MPSA42RL1 meet RoHS requirements?

Yes, the MPSA42RL1 is available in Pb-free version (MPSA42RL1G), compliant with RoHS Directive 2011/65/EU. The standard MPSA42RL1 may contain lead per exemption 7a; for RoHS-compliant designs, specify MPSA42RL1G and confirm material declarations via onsemi's official product change notices or Aetrix Electronics' certified compliance documentation.

MPSA42RL1 Specifications

Product attributes: Attribute value

Manufacturer:: onsemi

Series:: -

Package/Case:: TO-226-3, TO-92-3 Long Body, Formed Leads

Packaging:: Tape & Reel (TR)

Product Status:: Obsolete

Transistor Type:: NPN

Current - Collector (Ic) (Max):: 500 mA

Voltage - Collector Emitter Breakdown (Max):: 300 V

Vce Saturation (Max) @ Ib, Ic:: 500mV @ 2mA, 20mA

Current - Collector Cutoff (Max):: 100nA (ICBO)

DC Current Gain (hFE) (Min) @ Ic, Vce:: 25 @ 1mA, 10V

Power - Max:: 625 mW

Frequency - Transition:: 50MHz

Operating Temperature:: -55°C ~ 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: TO-92 (TO-226)

MPSA42RL1 FAQ

1.How can I place an order for MPSA42RL1 through Aetrix?

Please submit a Request for Quotation (RFQ) for MPSA42RL1 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 MPSA42RL1 reliable?

The price and inventory of MPSA42RL1 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MPSA42RL1 is usually 5 days.

3.What payment methods are accepted for MPSA42RL1?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MPSA42RL1 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for MPSA42RL1?

MPSA42RL1 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your MPSA42RL1 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 MPSA42RL1?

For technical support, including MPSA42RL1 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MPSA42RL1 requirements.

6.How does Aetrix verify that MPSA42RL1 is sourced from the original manufacturer or authorized distributors?

All MPSA42RL1 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 MPSA42RL1 meets industry standards.

7.What is the process for return or replacement of MPSA42RL1?

All MPSA42RL1 units undergo pre-shipment inspection (PSI). If there is an issue with MPSA42RL1, 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 MPSA42RL1 part is unused and in its original packaging.

Return procedure for MPSA42RL1:

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…