onsemi MPSA42RLRA

Overview

MPSA42RLRA from onsemi is an NPN silicon high-voltage transistor designed for switching and amplification in off-line power supplies, flyback converters, and voltage multiplier circuits. It features a 300 V_CEO, 500 mA continuous collector current, 625 mW power dissipation at T_A = 25°C, and DC current gain (h_FE) ≥25 at I_C = 1.0 mA, V_CE = 10 V - enabling reliable operation in high-impedance, low-current HV bias networks.

For engineers reviewing the MPSA42RLRA datasheet, pinout, applications, or equivalent options, key selection criteria include its 300 V breakdown rating, TO-92 package thermal limits (R_JA = 200°C/mW), saturation voltage behavior across temperature, and compatibility with discrete HV driver stages in AC/DC front-end designs.

Technical Context

The MPSA42RLRA operates as a general-purpose NPN bipolar junction transistor optimized for high-voltage, medium-current switching. Its V_(BR)CEO = 300 V and V_(BR)CBO = 300 V support direct connection to rectified line voltages up to ~210 V RMS. The device exhibits h_FE ≥25 at low I_C (1 mA) and maintains usable gain down to −55°C, making it suitable for cold-start HV biasing.

Thermal performance is defined by two dissipation ratings: 625 mW at T_A = 25°C (derated 5 mW/°C above ambient) and 1.5 W at T_C = 25°C (derated 12 mW/°C above case). This dual-rating structure reflects its intended use with heatsinking in higher-power configurations or lead-frame conduction in compact TO-92 layouts.

Key Specifications

Pinout & Package

Package: TO-92 (Case 29-11), molded plastic with 3 leads, JEDEC standard outline. Lead finish is matte tin (Pb-free per ordering suffix 'G'; MPSA42RLRA is standard SnPb).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MPSA43 and MPSA92, the MPSA42RLRA provides the highest voltage margin among TO-92 NPNs while maintaining lowest leakage and optimal gain at microampere-level currents - critical for energy-efficient HV startup and sensing circuits.

Availability

MPSA42RLRA is available at Aetrix Electronics and suitable for off-line power supply biasing, flyback converter startup circuits, and voltage multiplier stages requiring stable component supply with full traceability and long-term lifecycle support.

Supply support for MPSA42RLRA 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 supplier delivering energy-efficient, intelligent power and sensing solutions for automotive, industrial, cloud, medical, and IoT applications.

The MPSA42RLRA belongs to onsemi's Preferred Devices family of general-purpose transistors - engineered for reliability, broad operating temperature range (−55°C to +150°C), and consistent parametric performance across manufacturing lots.

FAQ

What is the maximum collector-emitter voltage rating for MPSA42RLRA?

The MPSA42RLRA has a guaranteed minimum V_(BR)CEO of 300 V at I_C = 1.0 mA and I_B = 0. This rating is validated per the onsemi datasheet Rev. 3 (June 2005) and applies under DC or low-duty-cycle pulsed conditions. Designers must ensure voltage transients remain within this limit, including safety margins for line surges and ringing in switching applications. The MPSA42RLRA is not rated for avalanche operation.

Does MPSA42RLRA have Pb-free packaging options?

Yes - the Pb-free variant is designated MPSA42RLRAG, which uses matte tin lead finish and complies with RoHS Directive 2011/65/EU. The MPSA42RLRA itself uses traditional SnPb termination. Both variants share identical electrical specifications, TO-92 package dimensions, and thermal characteristics; only the plating differs. No reflow profile changes are required when migrating from MPSA42RLRA to MPSA42RLRAG.

How does the DC current gain (h_FE) of MPSA42RLRA vary with collector current?

The MPSA42RLRA exhibits h_FE ≥25 at I_C = 1.0 mA, ≥40 at I_C = 10 mA, and ≥40 at I_C = 30 mA (all at V_CE = 10 V, T_A = 25°C). Gain peaks near 10–30 mA and declines at both lower and higher currents. For bias networks drawing <1 mA, designers should use the 25 minimum value in calculations; for switching applications at 20 mA, the typical h_FE exceeds 50, allowing conservative base drive design. The MPSA42RLRA datasheet confirms this trend across temperature.

Can MPSA42RLRA be used in place of MPSA43?

MPSA42RLRA is not a drop-in replacement for MPSA43 due to its higher 300 V V_CEO rating versus MPSA43's 200 V rating. While pinout and package are identical, substituting MPSA42RLRA into an MPSA43-design may introduce unnecessary cost and thermal overhead without functional benefit - unless the circuit actually stresses V_CE beyond 200 V. The MPSA42RLRA datasheet explicitly positions it as the higher-voltage sibling, not a functional upgrade.

What is the thermal resistance from junction to ambient for MPSA42RLRA?

The MPSA42RLRA has a specified R_JA of 200°C/mW when mounted on a standard FR-4 PCB with minimal copper (JEDEC Test Method JESD51-3). This means a 100 mW power dissipation causes a ~20°C junction-to-ambient rise. To improve thermal performance, designers should use thermal relief pads, internal copper planes, or external heatsinking - especially since the device also supports 1.5 W at T_C = 25°C. The MPSA42RLRA's R_JC is 83.3°C/mW, confirming case-conducted cooling is highly effective.