onsemi MPSA42ZL1

Overview

MPSA42ZL1 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 25°C ambient. It delivers DC current gain (h_FE) ≥25 at I_C = 1.0 mA and V_CE = 10 V, with V_CE(sat) ≤ 0.5 V at I_C/I_B = 10, suitable for high-voltage switching in flyback snubbers and relay drivers.

For engineers reviewing the MPSA42ZL1 datasheet, pinout, applications, or equivalent options, key selection criteria include verified V_CEO = 300 V, h_FE min of 25 at low bias, TO-92 pinout configuration (Emitter–Collector–Base), thermal resistance R_JA = 200°C/mW, and Pb-free availability in Ammo Pack packaging.

Technical Context

The MPSA42ZL1 operates as a discrete NPN bipolar junction transistor optimized for high-voltage linear and switching applications up to 300 V. Its structure supports stable gain across −55°C to +150°C junction temperature range and exhibits C_cb = 3.0 pF at V_CB = 20 V, enabling use in moderate-frequency amplifier stages.

It features low saturation voltage (V_CE(sat) ≤ 0.5 V) under I_C = 20 mA / I_B = 2 mA drive, and maintains V_BE(sat) ≤ 0.9 V under same conditions. The device's f_T = 50 MHz ensures usable bandwidth in signal conditioning and pulse amplification circuits without requiring RF-grade layout.

Key Specifications

Pinout & Package

Package: TO-92 (Case 29−11), molded plastic with 3-lead vertical mounting. Pin identification follows Style 1: Pin 1 = Emitter, Pin 2 = Base, Pin 3 = Collector.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MPSA42ZL1, MPSA42RL1 offers identical electrical performance in tape-and-reel form for pick-and-place lines, while BC639 provides higher gain and speed but lacks the 300 V rating required for mains-connected circuits - making MPSA42ZL1 irreplaceable in high-voltage isolation and snubber roles.

Availability

MPSA42ZL1 is available at Aetrix Electronics and suitable for switch-mode power supply snubbers, AC line voltage sensing circuits, and relay driver modules requiring stable component supply across industrial and embedded power designs.

Supply support for MPSA42ZL1 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 focused on energy-efficient electronics, delivering silicon solutions for automotive, industrial, cloud, and IoT applications.

The MPSA42ZL1 belongs to onsemi's Preferred Devices family of high-reliability general-purpose transistors, engineered for robustness in high-voltage switching and signal amplification where long-term parametric stability and wide temperature operation are critical.

FAQ

What is the maximum collector-emitter voltage rating for MPSA42ZL1?

The MPSA42ZL1 has a guaranteed minimum V_CEO rating of 300 Vdc under test condition I_C = 1.0 mA and I_B = 0. This rating is validated per the onsemi MPSA42/D datasheet Rev. 3 and applies to continuous DC operation. Transient spikes exceeding this value require external clamping. The MPSA42ZL1 must not be operated beyond its absolute maximum ratings to ensure reliability.

Is MPSA42ZL1 compatible with lead-free soldering processes?

Yes, the MPSA42ZL1 is offered in both standard and Pb-free versions (MPSA42ZL1G). Its TO-92 package meets JEDEC J-STD-020 moisture sensitivity level 1 and supports reflow profiles up to 260°C peak. The MPSA42ZL1G variant complies with RoHS Directive 2011/65/EU and is qualified for standard lead-free assembly without special flux or dwell time adjustments.

How does the DC current gain (h_FE) of MPSA42ZL1 vary with collector current?

The MPSA42ZL1 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 decreases at higher currents due to series resistance effects. Designers using MPSA42ZL1 should verify gain at their specific operating point using the Figure 3 h_FE vs. I_C curve in the official datasheet.

What is the thermal resistance from junction to ambient for MPSA42ZL1?

The MPSA42ZL1 has a specified R_JA of 200°C/mW when mounted on a standard FR-4 PCB with minimal copper area. This value assumes natural convection and no heatsink. In practice, adding 1 cm² of 2-oz copper pour beneath the emitter pad reduces R_JA by ~30%. For sustained 500 mA operation, thermal derating per the datasheet (5.0 mW/°C above 25°C) must be applied to avoid exceeding T_J(max) = +150°C.

Can MPSA42ZL1 replace MPSA43 in existing designs?

No - MPSA42ZL1 and MPSA43 are not interchangeable. The MPSA42ZL1 is rated for V_CEO = 300 V and V_CBO = 300 V, while MPSA43 is rated for 200 V in both parameters. Substituting MPSA42ZL1 for MPSA43 introduces unnecessary voltage overhead and may affect bias stability due to differing h_FE distributions. Always validate replacement with circuit simulation and worst-case stress analysis for the MPSA42ZL1.