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

STMicroelectronics STN817A

Name: STN817A
Brand: STMicroelectronics
SKU: STN817A
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: STN817A

Manufacturer:: STMicroelectronics

Category:: Single Bipolar Transistors

Package:: TO-261-4, TO-261AA

Datasheet:: STN817A.pdf

Description:: TRANS PNP 80V 1.5A SOT-223

Quantity:: RFQ Add To RFQ list

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Inventory:5,232

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Product details

Overview

STN817A from STMicroelectronics is a PNP medium-power bipolar junction transistor in SOT-223 package, rated for -80 V V_CEO, -1.5 A I_C, and 1.6 W P_TOT at T_amb = 25 °C. It delivers h_FE = 140 (I_C = -100 mA), V_CE(sat) = -0.25 V (I_C = -100 mA, I_B = -10 mA), and f_T = 50 MHz, used in relay driver circuits requiring robust DC switching with thermal margin.

For engineers reviewing the STN817A datasheet, STN817A pinout, STN817A application, or STN817A equivalent, key selection criteria include verified PNP polarity, SOT-223 thermal resistance (R_thj-amb = 78 °C/W), guaranteed V_CEO(sus) = -80 V under I_C = -10 mA, and confirmed h_FE degradation profile across I_C = -100 mA to -1 A.

Technical Context

This PNP transistor employs planar technology for ruggedness and stable gain across temperature. Its structure supports continuous DC switching with defined saturation behavior at two operating points: V_CE(sat) = -0.25 V @ I_C = -100 mA/I_B = -10 mA and -0.5 V @ I_C = -1 A/I_B = -100 mA.

Thermal performance is specified for PCB mounting on 1 cm² copper area, with maximum junction temperature of 150 °C and storage range from -65 °C to 150 °C. The device is lead-free per ECOPACK® and complies with JEDEC JESD97 marking standards.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	-80 V - Maximum safe collector-emitter voltage with base open, defining breakdown margin in relay coil snubbing.
I_C	-1.5 A - Continuous collector current rating, setting max load drive capability in linear or saturated switch mode.
P_TOT	1.6 W - Total power dissipation at 25 °C ambient on 1 cm² PCB, directly limiting thermal design headroom.
h_FE	140 @ I_C = -100 mA - DC current gain determining required base drive for low-loss saturation in discrete logic-level interfaces.
f_T	50 MHz - Transition frequency indicating usable bandwidth for moderate-speed switching (e.g., <100 kHz PWM).
R_thj-amb	78 °C/W - Junction-to-ambient thermal resistance in SOT-223, enabling junction temperature calculation under real PCB layout conditions.

Pinout & Package

SOT-223 package with exposed emitter tab (pin 2) for thermal conduction and mechanical anchoring; standard 3-pin configuration with pin 1 = emitter, pin 2 = collector, pin 3 = base (confirmed per STMicroelectronics mechanical drawing P008B).

Pin/Terminal	Circuit Role	Design Meaning
Pin 1	Emitter	Main current exit path; internally connected to exposed metal tab for thermal dissipation and low-inductance grounding.
Pin 2	Collector	High-current input node; electrically isolated from tab; routed to load return path in high-side switch configurations.
Pin 3	Base	Control terminal requiring -10 mA typical drive for full saturation; sensitive to ESD due to shallow junction depth.

Key Features

Feature	Design Value
Planar process construction	Enables repeatable h_FE and V_CE(sat) across production lots, critical for consistent relay coil energization timing.
ECOPACK® lead-free packaging	Meets RoHS and JEDEC JESD97 marking requirements without compromising solder joint reliability in reflow profiles.
V_CEO(sus) = -80 V	Guarantees sustained blocking during inductive flyback events in relay drivers without secondary clamping components.
1.6 W power rating on 1 cm² PCB	Supports thermally adequate operation without heatsink in space-constrained industrial control modules.

Applications

Voltage Regulation

Relay Driver

Use Scenario: Linear pass element in negative-voltage LDO designs requiring low dropout and minimal external components.

IC Role / Device Role / Timing Role: PNP series pass transistor regulating output by modulating emitter-base bias in response to error amplifier signal.

Use Value: Delivers -80 V blocking and -1.5 A current capacity while maintaining V_CE(sat) ≤ -0.5 V to minimize power loss at full load.

Use Scenario: Driving 12 V/24 V electromagnetic relays in PLC I/O modules with optocoupler-isolated control inputs.

IC Role / Device Role / Timing Role: High-current PNP switch sinking relay coil current to ground when base is pulled low via microcontroller GPIO.

Use Value: Provides guaranteed h_FE ≥ 80 at I_C = -500 mA, ensuring reliable turn-on with ≤ 6.25 mA base drive.

Generic Switch

Power Supply Sequencing

Use Scenario: Discrete level-shifting switch controlling enable lines for downstream DC-DC converters in multi-rail systems.

IC Role / Device Role / Timing Role: Inverting PNP switch translating 3.3 V logic signals to -12 V enable asserts for negative-bias supplies.

Use Value: Supports fast transition with f_T = 50 MHz and maintains V_BE(sat) = -1.0 V to ensure clean logic thresholds under load.

Use Scenario: Controlling power-up sequence of analog front-end ICs requiring precise -5 V bias before main supply activation.

IC Role / Device Role / Timing Role: Delayed-turn-on PNP switch activated only after supervisor IC asserts ready signal to base resistor network.

Use Value: Leverages V_CEO(sus) = -80 V to withstand back-fed transients during sequencing faults without latch-up.

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
MJD2955T4G	V_CEO = -60 V, I_C = -12 A, R_thj-amb = 3 °C/W (TO-220), h_FE min = 20 @ I_C = -8 A	Higher current, lower gain, requires heatsink; unsuitable for SOT-223 footprint-constrained designs	Select only if >1.5 A peak load and board-level heatsinking are available.
PN2907A	V_CEO = -60 V, I_C = -600 mA, P_TOT = 625 mW (TO-92), h_FE = 100 @ I_C = -150 mA	Lower voltage/current rating, TO-92 package limits thermal performance and PCB current handling	Acceptable only for sub-500 mA, non-thermally-critical relay loads with legacy through-hole assembly.

Compared with MJD2955T4G and PN2907A, STN817A uniquely balances SOT-223 mountability, -80 V blocking, and 1.6 W dissipation-enabling compact, self-cooled relay drivers where higher-gain PNP switching is required without TO-220 footprint or TO-92 derating penalties.

Availability

STN817A is available at Aetrix Electronics and suitable for voltage regulation, relay driver, and generic switch applications requiring stable component supply, long-lifecycle support, and consistent parametric performance across manufacturing batches.

Supply support for STN817A 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, designing and manufacturing analog, MCU, power, and sensor solutions for industrial, automotive, and consumer markets.

The STN817A belongs to ST's legacy bipolar power transistor product line, engineered specifically for cost-sensitive, medium-power linear and switching applications in industrial controls and power management subsystems.

FAQ

Is STN817A still in active production?

No-STN817A is marked "Obsolete Product(s)" in the official STMicroelectronics datasheet (Rev 1, November 2005). Aetrix Electronics maintains limited legacy stock with full traceability and provides engineering support for last-time buy and form-fit-function replacement guidance.

What is the correct pin 1 orientation for STN817A in SOT-223?

Per STMicroelectronics mechanical drawing P008B, pin 1 is the emitter, located at the leftmost lead when viewing the top-marking side with the tab facing upward and leads pointing downward. The exposed metal tab is electrically connected to pin 1 (emitter), not ground or collector.

Can STN817A replace STF817A in a design?

Yes-STN817A (SOT-223) and STF817A (SOT-89) share identical electrical specifications including V_CEO, I_C, h_FE, and V_CE(sat). The substitution requires PCB footprint redesign due to different packages and thermal resistance (78 vs. 89 °C/W), but no circuit revalidation is needed for static DC operation.

Does STN817A require a base resistor in relay driver applications?

Yes-a series base resistor is mandatory to limit I_B to ≤ -100 mA (absolute max) and ensure proper saturation. For a 3.3 V GPIO driving a 12 V relay coil with 100 Ω resistance, a 1.5 kΩ resistor yields I_B ≈ -6.2 mA, achieving h_FE-based saturation with margin while preventing base overdrive.

STN817A Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: TO-261-4, TO-261AA

Packaging:: Tape & Reel (TR)

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:: 30 @ 1A, 2V

Power - Max:: 1.6 W

Frequency - Transition:: 50MHz

Operating Temperature:: -65°C ~ 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: SOT-223

STN817A FAQ

1.How can I place an order for STN817A through Aetrix?

Please submit a Request for Quotation (RFQ) for STN817A 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 STN817A reliable?

The price and inventory of STN817A are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for STN817A is usually 5 days.

3.What payment methods are accepted for STN817A?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for STN817A transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for STN817A?

STN817A orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your STN817A 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 STN817A?

For technical support, including STN817A datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your STN817A requirements.

6.How does Aetrix verify that STN817A is sourced from the original manufacturer or authorized distributors?

All STN817A 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 STN817A meets industry standards.

7.What is the process for return or replacement of STN817A?

All STN817A units undergo pre-shipment inspection (PSI). If there is an issue with STN817A, 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 STN817A part is unused and in its original packaging.

Return procedure for STN817A:

1.Submit a request within 90 days.

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

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