onsemi MPSW45A

Overview

MPSW45A from onsemi is an NPN silicon Darlington transistor in a TO-92 package, rated for 50 V_CE, 1.0 A continuous collector current, and 1.0 W dissipation at T_A = 25°C. It delivers high DC current gain (h_FE = 4,000–150,000) with low saturation voltage (V_CE(sat) ≤ 1.5 V at I_C = 1.0 A, I_B = 2.0 mA), enabling efficient switching in low-voltage relay drivers and power interface circuits.

For engineers reviewing the MPSW45A datasheet, pinout, applications, or equivalent options, key selection criteria include its 50 V_CES rating, Darlington architecture for high current amplification, TO-92 mechanical compatibility, thermal resistance (R_θJA = 125°C/W), and Pb-free packaging compliance per onsemi's Rev. 4 specification.

Technical Context

The MPSW45A implements a monolithic NPN Darlington pair with integrated base-emitter resistor network absent - external base drive is required. Its high h_FE enables microampere-level base current control of 1 A loads, while f_T = 100 MHz supports moderate-speed switching up to ~100 kHz under resistive loads.

Thermal design relies on R_θJC = 50°C/W and R_θJA = 125°C/W, limiting continuous operation to ≤800 mW at 70°C ambient without heatsinking. Safe operating area (SOA) curves confirm single-pulse capability up to 700 mA at 40 V within 1 ms, constrained by second breakdown limits.

Key Specifications

Pinout & Package

Package: TO-92 (Case 29-10), through-hole, straight or bent lead options, Pb-free (MPSW45AZL1G variant). Dimensions comply with ON Semiconductor Issue D (05 MAR 2021).

Key Features

Applications

Equivalent & Alternatives

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

Compared with ULN2003A and MPSW45, the MPSW45A provides higher voltage headroom (50 V vs. 40 V or 50 V array limit), single-device simplicity for high-current loads, and TO-92 ease of hand-soldering - making it optimal for discrete 1 A switching where space and BOM count are constrained.

Availability

MPSW45A is available at Aetrix Electronics and suitable for industrial relay drivers, automotive interior lighting control, low-voltage LED matrix switching, and small-solenoid actuation requiring stable component supply and long-term obsolescence management.

Supply support for MPSW45A 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 specializing in energy-efficient power management, analog, sensor, and connectivity solutions for automotive, industrial, and cloud infrastructure markets.

The MPSW45A belongs to onsemi's legacy discrete transistor family designed for robust, cost-effective switching in industrial controls and automotive body electronics where reliability, thermal stability, and Pb-free compliance are mandatory.

FAQ

What is the maximum continuous collector current rating for the MPSW45A?

The MPSW45A is rated for 1.0 A continuous collector current (I_C) at T_A = 25°C. Derating applies above 25°C at 8.0 mW/°C for ambient-limited operation or 20 mW/°C for case-limited operation. At 70°C ambient, maximum continuous I_C drops to approximately 640 mA to maintain junction temperature below 150°C. This rating is confirmed in the "Maximum Ratings" table of the official MPSW45/D datasheet Rev. 4.

Does the MPSW45A have integrated base resistors or protection diodes?

No, the MPSW45A is a bare Darlington transistor without integrated base resistors or clamp diodes. External components must be added: a series base resistor to set I_B, and a flyback diode across inductive loads to suppress V_CE spikes. This differs from array devices like ULN2003A. The MPSW45A's schematic symbol and electrical characteristics tables in the datasheet confirm absence of internal passive components.

What is the typical DC current gain (h_FE) of the MPSW45A at 1.0 A collector current?

The MPSW45A exhibits h_FE = 4,000 (minimum) to 150,000 (maximum) at I_C = 1.0 A, V_CE = 5.0 V, and T_A = 25°C, per the "Electrical Characteristics" table. Typical values cluster near 15,000–25,000 in production lots. This wide range necessitates design margining - e.g., sizing the base resistor for worst-case h_FE = 4,000 to ensure saturation under all conditions.

Can the MPSW45A replace the MPSW45 in existing designs?

Yes, the MPSW45A is a direct upgrade to the MPSW45 with identical pinout, package, and thermal characteristics, but improved V_CES (50 V vs. 40 V) and V_CBO (60 V vs. 50 V). No PCB changes are required. However, verify that system transients remain within the MPSW45A's 50 V rating - especially in 24 V industrial systems with load dump events exceeding 40 V. The MPSW45A datasheet explicitly positions it as a higher-voltage variant.

What is the thermal resistance junction-to-ambient (R_θJA) for the MPSW45A in a standard TO-92 footprint?

The MPSW45A has R_θJA = 125°C/W when mounted on a standard FR-4 PCB with minimal copper (JEDEC standard test board). This value assumes no heatsink or thermal vias. Adding 1 in² of 2-oz copper pour with 4 thermal vias reduces R_θJA to ~65°C/W. The 125°C/W figure is specified in the "Thermal Characteristics" section of the MPSW45/D datasheet and governs maximum power dissipation at elevated ambient temperatures.