STMicroelectronics STR2550

Overview

STR2550 from STMicroelectronics is a high-voltage fast-switching PNP power transistor in SOT-23 package, rated for -500 V V_CEO, -0.5 A continuous collector current, and 500 mW power dissipation at 25 °C. It features excellent h_FE linearity up to 50 mA and is optimized for LED driving circuits requiring robust voltage blocking and stable gain under pulsed operation.

For engineers reviewing the STR2550 datasheet, STR2550 pinout, STR2550 application, or STR2550 equivalent, key selection criteria include its -500 V breakdown rating, low -0.2 V V_CE(sat) at -20 mA/-2 mA drive, cellular emitter structure for enhanced RBSOA, and SOT-23 surface-mount compatibility in space-constrained LED driver designs.

Technical Context

This device uses high-voltage multi-epitaxial planar technology with planar edge termination and a cellular emitter layout to achieve fast switching while maintaining wide reverse-biased safe operating area (RBSOA). Its negative-polarity electrical characteristics reflect PNP operation: all voltages are negative, currents are negative, and saturation behavior is specified at defined h_FE conditions.

The transistor supports pulsed operation (300 µs, ≤2% duty cycle) for transient load handling and exhibits stable h_FE of 100–300 across -1 mA to -50 mA I_C, with degradation only below 10 at -100 mA - enabling predictable current amplification in constant-current LED bias stages.

Key Specifications

Pinout & Package

SOT-23 plastic package: 3-pin, surface-mount, tape-and-reel compatible; dimensions per DS8711 Rev 6 (A2 = 1.10–1.20 mm, D = 2.826–3.026 mm, E = 2.60–3.00 mm).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar high-voltage PNP switching applications.

Compared with MMBT2907A and PN2907A, STR2550 uniquely delivers -500 V blocking in SOT-23, enabling high-voltage LED drivers without discrete HV MOSFETs or external protection, while maintaining manufacturability and thermal performance.

Availability

STR2550 is available at Aetrix Electronics and suitable for automotive interior lighting, industrial status indicators, and outdoor LED signage requiring stable component supply and long-term production continuity.

Supply support for STR2550 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

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, designing and manufacturing silicon solutions for smart mobility, power, and sensing applications.

STR2550 belongs to ST's high-voltage bipolar transistor product line, engineered specifically for robust, cost-effective switching in LED lighting, industrial controls, and power supply feedback circuits.

FAQ

What is the maximum safe operating voltage for STR2550 in continuous DC mode?

The STR2550 is rated for -500 V V_CEO with IB = 0 A and IC = -1 mA, and -500 V V_CBO with IE = 0 A. In continuous DC operation, it must be operated within these absolute maximum ratings, with design margin applied per IEC 61000-4-5 surge standards. Derating is recommended above 350 V for long-term reliability.

Can STR2550 be used in linear (analog) LED current regulation?

Yes - STR2550 exhibits excellent h_FE linearity up to -50 mA and stable V_BE(on) (-1.1 V at -50 mA), making it suitable for precision linear current sources. Its -0.3 V V_CE(sat) at -50 mA ensures low dropout and minimal power loss in analog dimming stages.

Is STR2550 pin-compatible with NPN counterparts like STR1550?

No - STR2550 is a PNP device with pinout E-B-C (pins 2-1-3), while STR1550 is its NPN complement with pinout C-B-E. Direct substitution would invert polarity and cause circuit malfunction; board layout and bias network must be redesigned for PNP vs. NPN topology.

Does STR2550 require a heatsink in standard SOT-23 mounting?

No external heatsink is required under typical conditions: at 25 °C ambient and 500 mW dissipation, R_thJA = 250 °C/W yields ΔT = 125 °C, resulting in T_J = 150 °C - exactly at maximum rating. For reliability, limit continuous power to ≤300 mW or increase PCB copper area beyond 1 cm².