STMicroelectronics STF817A

Overview

STF817A from STMicroelectronics is a PNP medium-power bipolar junction transistor in SOT-89 package, rated for V_CEO = –80 V, I_C = –1.5 A, and P_TOT = 1.4 W at T_amb = 25 °C, used as a relay driver or voltage regulation switch in industrial control circuits.

For engineers reviewing the STF817A datasheet, STF817A pinout, STF817A application, or STF817A equivalent, key selection criteria include its negative-polarity switching capability, DC current gain (h_FE = 140 at I_C = –100 mA), saturation voltage (V_CE(sat) = –0.25 V), thermal resistance (R_thj-amb = 89 °C/W), and lead-free ECOPACK® compliance.

Technical Context

The STF817A operates as a single PNP BJT with planar silicon construction, optimized for medium-power linear and switching applications. Its base-emitter and collector-base junctions are rated to –5 V and –80 V respectively, supporting robust blocking in high-side switch configurations.

It delivers h_FE ≥ 30 at I_C = –1 A and V_CE = –2 V, with f_T = 50 MHz under pulsed conditions (I_C = –0.1 A, V_CE = –10 V), enabling stable operation in low-frequency power control and analog feedback loops.

Key Specifications

Pinout & Package

SOT-89 package: 3-pin surface-mount plastic case with exposed emitter tab for thermal and electrical connection; standardized footprint per JEDEC TO-243AA.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar PNP medium-power switching applications.

Compared with MJD2955T4G and ZTX753, the STF817A uniquely balances SOT-89 form factor, –80 V blocking, and 1.4 W dissipation-making it optimal for compact 24 V industrial controls where thermal management and board space are jointly constrained.

Availability

STF817A is available at Aetrix Electronics and suitable for industrial relay drivers, negative-voltage regulators, and power supply sequencing circuits requiring stable component supply and long-term manufacturability.

Supply support for STF817A 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, specializing in power management, analog, microcontrollers, and automotive ICs.

The STF817A belongs to ST's legacy bipolar power transistor family, designed specifically for cost-sensitive, medium-power industrial switching and regulation where ruggedness and proven reliability outweigh advanced integration.

FAQ

Is the STF817A RoHS-compliant and lead-free?

Yes. The STF817A uses ST's ECOPACK® packaging with lead-free second-level interconnect, compliant with RoHS Directive 2011/65/EU and JEDEC Standard JESD97. The inner box label indicates the lead-free category and maximum soldering temperature limits.

What is the recommended PCB layout for thermal performance?

Mount the STF817A on a minimum 1 cm² copper area connected to the emitter tab, using multiple thermal vias to internal ground planes. Avoid routing high-current traces near the base pad to prevent coupling noise into the control node.

Can the STF817A replace the STN817A in a design?

No. Although electrically identical, the STF817A uses SOT-89 while the STN817A uses SOT-223-different footprints, thermal resistances (89 vs. 78 °C/W), and mechanical dimensions. Board redesign is required for substitution.

Does the STF817A support pulse operation beyond its DC ratings?

Yes. It supports I_CM = –2 A peak collector current and I_BM = –0.6 A peak base current for pulse widths <5 ms and duty cycle ≤1.5%, provided average power remains within 1.4 W and junction temperature stays below 150 °C.