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Home > Products > Discrete Semiconductor Products > Transistors > Bipolar (BJT) > Single Bipolar Transistors

STMicroelectronics STX817A

Name: STX817A
Brand: STMicroelectronics
SKU: STX817A
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: STX817A

Manufacturer:: STMicroelectronics

Category:: Single Bipolar Transistors

Package:: TO-226-3, TO-92-3 (TO-226AA)

Datasheet:: STX817A.pdf

Description:: TRANS PNP 80V 1.5A TO-92-3

Quantity:: RFQ Add To RFQ list

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Inventory:4,551

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Product details

Overview

STX817A from STMicroelectronics is a PNP medium-power bipolar junction transistor in TO-92 package, rated for -80 V V_CEO, -1.5 A I_C, 0.9 W P_tot, with h_FE = 140 (at I_C = -100 mA), and f_T = 50 MHz. It serves as a high-voltage switch or relay driver in industrial power control circuits.

For engineers reviewing the STX817A datasheet, STX817A pinout, STX817A application, or STX817A equivalent, key selection criteria include its -80 V blocking capability, -1.5 A continuous collector current, saturation voltage of -0.25 V at -100 mA/-10 mA drive, rugged planar construction, and TO-92 through-hole compatibility for legacy PCB designs.

Technical Context

This PNP transistor uses planar technology to achieve high ruggedness and stable gain across temperature. Its -80 V V_CEO and -80 V V_CBO support operation in high-side switching configurations up to 80 V rail systems, while the -1.5 A I_C rating enables direct driving of small relays and solenoids.

The device exhibits low V_CE(sat) (-0.25 V typical at -100 mA/-10 mA) and moderate f_T (50 MHz), indicating suitability for DC and low-frequency switching (≤10 kHz), not RF amplification. Thermal resistance R_thj-amb = 139 °C/W confirms need for heatsinking above ~300 mW dissipation.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	-80 V - supports high-side switching in 48–72 V industrial power rails
I_C	-1.5 A - drives relays, small solenoids, or logic-level loads directly
P_tot	0.9 W at T_amb = 25°C - requires thermal derating above 25°C ambient
h_FE	140 min at I_C = -100 mA - ensures reliable base drive margin for saturated switching
V_CE(sat)	-0.25 V max at I_C = -100 mA / I_B = -10 mA - minimizes conduction loss in on-state
f_T	50 MHz - sufficient for <10 kHz switching but not RF or fast PWM
R_thj-amb	139 °C/W - limits usable power without heatsink to ~300 mW at 70°C ambient

Pinout & Package

TO-92 package: 3-lead through-hole plastic case with standard lead spacing (E = 3.30–3.94 mm, e = 2.41–2.67 mm), designed for wave soldering and manual assembly. Pin identification follows JEDEC TO-92 outline: viewed from flat side with leads down, left-to-right = Emitter (E), Base (B), Collector (C).

Pin/Terminal	Circuit Role	Design Meaning
Emitter (E)	Current sink terminal for PNP operation	Connected to higher potential rail; defines reference for base bias and load return path
Base (B)	Control input for minority-carrier injection	Requires negative current relative to emitter to turn on; typical drive: -10 mA for 100 mA load
Collector (C)	Output current terminal	Connected to load; voltage swing limited to -80 V max relative to emitter

Key Features

Feature	Design Value
Planar silicon process	Enables consistent h_FE distribution and improved thermal stability vs. epitaxial alternatives
ECOPACK® lead-free interconnect	Complies with RoHS Directive 2002/95/EC and JEDEC JESD97 marking requirements
V_CEO(sus) = -80 V	Guarantees safe operation under transient overvoltage in unregulated 48 V supply lines
TO-92 mechanical standardization	Ensures drop-in replacement in legacy designs using MIL-STD-1835B-compliant footprints

Applications

Voltage Regulation

Relay Driver

Use Scenario: Linear pass element in adjustable 5–30 V negative-output regulators using LM337-based topologies.

IC Role / Device Role / Timing Role: PNP series pass transistor regulating output by sinking current from error amplifier.

Use Value: -80 V V_CEO allows headroom for 24 V input with 15 V dropout; -0.25 V V_CE(sat) reduces thermal load at 500 mA.

Use Scenario: Driving 12 V/400 mW electromagnetic relay coils in PLC I/O modules.

IC Role / Device Role / Timing Role: High-side switch controlling coil energization via microcontroller GPIO.

Use Value: -1.5 A I_C exceeds relay hold current (120 mA); h_FE ≥140 ensures full saturation with 1 mA base drive.

Generic Switch

Industrial Power Sequencing

Use Scenario: Enabling/disabling auxiliary 5 V standby rails in multi-rail embedded power supplies.

IC Role / Device Role / Timing Role: Low-speed on/off switch controlled by enable signal from supervisor IC.

Use Value: TO-92 footprint simplifies layout; -80 V rating accommodates back-EMF from inductive loads during turn-off.

Use Scenario: Controlling power-up sequence of analog front-end and digital core in sensor nodes.

IC Role / Device Role / Timing Role: Delayed activation switch triggered by RC timer network on base.

Use Value: Predictable h_FE and low leakage (ICES ≤ -500 µA) ensure precise timing window and minimal standby drain.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
BC807-40	SMD SOT-23, lower V_CEO (-45 V), lower I_C (-500 mA), h_FE = 250–630	Not suitable for >45 V rails or >500 mA loads; requires PCB redesign for SMT	Select only if space-constrained and voltage/current demands are reduced
MJD2955T4G	TO-220, higher P_tot (15 W), V_CEO = -60 V, I_C = -12 A	Over-specified for same function; requires heatsink and larger board area	Choose only when thermal budget exceeds 0.9 W or load current >1.5 A

Compared with BC807-40, STX817A offers higher voltage margin and through-hole compatibility; versus MJD2955T4G, it provides compact size and lower cost for sub-1 A, 80 V-class switching where thermal load stays below 0.9 W.

Availability

STX817A is available at Aetrix Electronics and suitable for voltage regulation, relay driver, and generic switch applications requiring stable component supply in legacy through-hole manufacturing environments.

Supply support for STX817A 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 analog, digital, and mixed-signal ICs and discrete devices for industrial, automotive, and consumer markets.

The STX817A belongs to ST's general-purpose bipolar transistor product line, engineered for robust, cost-effective switching in industrial control, power management, and legacy equipment replacement.

FAQ

Is STX817A still in active production?

No - STMicroelectronics has marked STX817A as obsolete per its official documentation (Rev 2, Jan 2007). However, Aetrix Electronics maintains verified legacy stock with full traceability and supports extended-life procurement for industrial maintenance and repair programs.

Can STX817A replace STX817?

Yes - STX817A is the enhanced version of STX817, with revised minimum h_FE specification (140 vs. earlier 100). Electrical ratings, pinout, and package are identical; it is a direct drop-in upgrade for all STX817 designs.

What is the maximum safe operating frequency for STX817A?

While f_T = 50 MHz, the device is characterized for DC and low-frequency switching only. Safe hard-switching operation is limited to ≤10 kHz due to stored charge and minority-carrier lifetime; faster edges risk incomplete turn-off and secondary breakdown.

Does STX817A require a base resistor in switching applications?

Yes - a current-limiting base resistor is mandatory to prevent excessive I_B (> -0.3 A absolute max). For -100 mA I_C, a 1 kΩ resistor from 5 V logic provides -4.3 mA I_B, ensuring h_FE-based saturation while staying within safe operating area.

STX817A Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: TO-226-3, TO-92-3 (TO-226AA)

Packaging:: Bag

Product Status:: Obsolete

Transistor Type:: PNP

Current - Collector (Ic) (Max):: 1.5 A

Voltage - Collector Emitter Breakdown (Max):: 80 V

Vce Saturation (Max) @ Ib, Ic:: 500mV @ 100mA, 1A

Current - Collector Cutoff (Max):: 1mA

DC Current Gain (hFE) (Min) @ Ic, Vce:: 25 @ 1A, 2V

Power - Max:: 900 mW

Frequency - Transition:: 50MHz

Operating Temperature:: 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: TO-92-3

STX817A FAQ

1.How can I place an order for STX817A through Aetrix?

Please submit a Request for Quotation (RFQ) for STX817A on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.

2.Are the price and stock information for STX817A reliable?

The price and inventory of STX817A are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for STX817A is usually 5 days.

3.What payment methods are accepted for STX817A?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for STX817A transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for STX817A?

STX817A orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your STX817A order is processed, you will receive an email with the shipment details and tracking number.

Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.

5.How can I obtain technical support or documentation for STX817A?

For technical support, including STX817A datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your STX817A requirements.

6.How does Aetrix verify that STX817A is sourced from the original manufacturer or authorized distributors?

All STX817A products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that STX817A meets industry standards.

7.What is the process for return or replacement of STX817A?

All STX817A units undergo pre-shipment inspection (PSI). If there is an issue with STX817A, returns or replacements are accepted under the following conditions:

1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.

2.The issue is reported within 90 days of delivery.

3.The STX817A part is unused and in its original packaging.

Return procedure for STX817A:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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