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

Diodes Incorporated ZTX550STOA

Name: ZTX550STOA
Brand: Diodes Incorporated
SKU: ZTX550STOA
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: ZTX550STOA

Manufacturer:: Diodes Incorporated

Category:: Single Bipolar Transistors

Package:: E-Line-3, Formed Leads

Datasheet:: ZTX550STOA.pdf

Description:: TRANS PNP 45V 1A E-LINE

Quantity:: RFQ Add To RFQ list

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Inventory:5,010

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Product details

Overview

ZTX550STOA from Diodes Incorporated is a PNP medium-power bipolar junction transistor in E-Line (TO-92 compatible) package, rated for -80V collector-base voltage, -1A continuous collector current, and 1W power dissipation at +25°C ambient. It operates up to +200°C junction temperature and is used in DC-DC converters, LCD backlight drivers, and emergency lighting circuits where high-voltage PNP switching with robust thermal capability is required.

For engineers reviewing the ZTX550STOA datasheet, ZTX550STOA pinout, ZTX550STOA application, or ZTX550STOA equivalent, key selection criteria include its -65V V_CEO, -350mV V_CE(sat) at -150mA/-15mA, h_FE range of 50–150 at -1A, f_T = 150MHz, and E-Line mechanical compatibility with TO-92 footprints.

Technical Context

This PNP transistor features a high-voltage breakdown rating (BV_CBO = -80V, BV_CEO = -65V), enabling use in off-line or boost-stage switching where collector swings below ground. Its -1A I_C rating and 1W PD support sustained medium-power amplification or switching without forced cooling.

Thermal design is supported by R_θJA = 175°C/W (min pad layout) and R_θJL = 63.75°C/W, allowing direct lead-to-PCB heat conduction. The device meets JEDEC reliability standards and is fully RoHS-compliant, halogen- and antimony-free ("Green").

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	-65 V - Maximum allowable collector-emitter voltage before avalanche; enables use in 48V+ supply rails or flyback snubbers
I_C	-1 A - Continuous DC collector current capacity; supports medium-power load switching without derating at T_J ≤ 125°C
V_CE(sat)	-350 mV @ -150mA/-15mA - Low saturation voltage reduces conduction loss in linear or saturated-switching applications
h_FE	50–150 @ -1A/-10V - Current gain range ensures predictable base drive requirements across production lots
f_T	150 MHz @ -10V/-150mA - Sufficient bandwidth for audio-frequency amplification and PWM switching up to ~10MHz
T_J max	+200°C - Enables operation in under-hood automotive or enclosed industrial environments without thermal shutdown
R_θJL	63.75°C/W - Low junction-to-lead thermal resistance allows effective heat transfer through collector lead to PCB copper

Pinout & Package

E-Line package: molded plastic, TO-92 compatible outline (D = 4.57mm, E = 3.90mm, L = 13.50mm), matte tin-plated leads, weight ≈ 0.159g. UL 94V-0 rated compound.

Pin/Terminal	Circuit Role	Design Meaning
Emitter (E)	Current source terminal for PNP operation	Connected to higher potential rail; carries full load current; requires low-impedance return path
Collector (C)	Current sink terminal	Typically tied to load and ground-return path; must withstand full V_CEO during cutoff
Base (B)	Control input for minority-carrier injection	Driven negative relative to emitter to turn on; requires current-limited bias network per h_FE and I_C

Key Features

Feature	Design Value
High-voltage PNP structure	BV_CBO = -80V supports robust operation in high-side switch or inductive load configurations
1W power dissipation	Enables self-contained operation in space-constrained DC-DC stages without heatsinking
JEDEC-qualified reliability	Validated per AEC-Q stress protocols; suitable for industrial control and lighting systems requiring long-term stability
Halogen- and antimony-free "Green" construction	Meets IEC 61249-2-21 and IPC-4101D; eliminates toxic flame retardants in PCB assembly

Applications

LCD Backlight Converter

Emergency Lighting Driver

Use Scenario: Boost-mode LED driver supplying 30–60V to parallel white LED strings in thin-panel displays.

IC Role / Device Role / Timing Role: PNP switch controlling primary-side current in discrete inductor-based boost topology.

Use Value: -65V V_CEO safely clamps inductive kickback; -350mV V_CE(sat) minimizes conduction loss at 500mA peak.

Use Scenario: Battery-backed constant-current source powering high-brightness LEDs during AC mains failure.

IC Role / Device Role / Timing Role: Medium-power PNP pass transistor regulating current through LED load via feedback-controlled base drive.

Use Value: 1W PD and +200°C T_J allow continuous operation in sealed enclosures without thermal throttling.

DC-DC Buck-Boost Stage

Industrial Sensor Signal Conditioning

Use Scenario: Discrete buck-boost converter generating ±12V from 24V rail in programmable logic controller (PLC) I/O modules.

IC Role / Device Role / Timing Role: PNP transistor in synchronous rectifier or active clamp circuit managing energy transfer timing.

Use Value: 150MHz f_T ensures stable switching at 500kHz PWM frequency with minimal phase lag.

Use Scenario: Precision current source driving 4–20mA loop transmitters in hazardous-area temperature sensors.

IC Role / Device Role / Timing Role: Linear-mode PNP output stage delivering regulated loop current with low thermal drift.

Use Value: Tight h_FE spread (50–150) and -55°C to +200°C operating range ensure calibration stability across environmental extremes.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
ZTX551	Same E-Line package, identical pinout, but released status vs. ZTX550STOA's obsolete designation; shares all electrical specs including -65V V_CEO, -1A I_C, and 1W PD	Direct functional replacement; no redesign needed for existing ZTX550STOA layouts	Select ZTX551 for new designs or inventory replenishment due to active production status and full documentation support
MJD2955G	TO-220 package, -60V V_CEO, -10A I_C, 75W PD - significantly higher power handling but larger footprint and different thermal interface	Suitable only where board space permits TO-220 and higher current/thermal margin is required	Choose only when ZTX550STOA's 1A/1W rating is insufficient and mechanical redesign is acceptable

Compared with ZTX550STOA, ZTX551 offers identical performance in an actively manufactured version, while MJD2955G provides higher current and power at the cost of size and layout compatibility - making ZTX551 the preferred drop-in alternative for continuity, and MJD2955G a niche upgrade for thermally demanding cases.

Availability

ZTX550STOA is available at Aetrix Electronics and suitable for LCD backlight converters, emergency lighting drivers, and DC-DC buck-boost stages requiring stable component supply and legacy-design continuity.

Supply support for ZTX550STOA 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

Diodes Incorporated is a global manufacturer of discrete semiconductors and analog ICs, headquartered in Plano, Texas, with design, manufacturing, and sales operations across Asia, Europe, and the Americas.

ZTX550/ZTX551 belongs to Diodes' general-purpose bipolar transistor product line, engineered for cost-sensitive, medium-power linear and switching applications in lighting, power conversion, and industrial controls where reliability and JEDEC compliance are essential.

FAQ

Is ZTX550STOA still in active production?

No - ZTX550STOA is marked obsolete in Diodes' official ordering information. The ZTX551 is the designated replacement with identical electrical specifications, E-Line packaging, and active production status. Aetrix Electronics maintains limited legacy stock of ZTX550STOA for design continuity but recommends transitioning to ZTX551 for new builds.

What is the correct pinout orientation for ZTX550STOA in E-Line package?

When viewing the flat face of the E-Line package with the leads pointing downward and the marking "ZTX550" visible, the left-to-right pin order is Emitter (E), Collector (C), Base (B). This matches the standard TO-92 pinout configuration and is confirmed in Diodes' DS33273 Rev. 2, page 2.

Can ZTX550STOA be used in automotive applications?

ZTX550STOA itself is not AEC-Q qualified. Diodes offers automotive-grade variants (e.g., ZTX551Q) with AEC-Q101 qualification, PPAP capability, and IATF 16949 manufacturing - these are explicitly listed in Diodes' Automotive Products portal. For automotive use, ZTX551Q must be selected instead of ZTX550STOA.

How does thermal performance differ between ZTX550STOA and ZTX551?

There is no thermal specification difference: both share identical R_θJA = 175°C/W (min pad), R_θJL = 63.75°C/W, and T_J = -55°C to +200°C. The datasheet confirms identical thermal characteristics across ZTX550 and ZTX551, as they share the same E-Line package construction and silicon process.

ZTX550STOA Specifications

Product attributes: Attribute value

Manufacturer:: Diodes Incorporated

Series:: -

Package/Case:: E-Line-3, Formed Leads

Packaging:: Tape & Reel (TR)

Product Status:: Obsolete

Transistor Type:: PNP

Current - Collector (Ic) (Max):: 1 A

Voltage - Collector Emitter Breakdown (Max):: 45 V

Vce Saturation (Max) @ Ib, Ic:: 250mV @ 15mA, 150mA

Current - Collector Cutoff (Max):: 100nA (ICBO)

DC Current Gain (hFE) (Min) @ Ic, Vce:: 100 @ 150mA, 10V

Power - Max:: 1 W

Frequency - Transition:: 150MHz

Operating Temperature:: -55°C ~ 200°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: E-Line (TO-92 compatible)

ZTX550STOA FAQ

1.How can I place an order for ZTX550STOA through Aetrix?

Please submit a Request for Quotation (RFQ) for ZTX550STOA 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 ZTX550STOA reliable?

The price and inventory of ZTX550STOA are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for ZTX550STOA is usually 5 days.

3.What payment methods are accepted for ZTX550STOA?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for ZTX550STOA transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for ZTX550STOA?

ZTX550STOA orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your ZTX550STOA 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 ZTX550STOA?

For technical support, including ZTX550STOA datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your ZTX550STOA requirements.

6.How does Aetrix verify that ZTX550STOA is sourced from the original manufacturer or authorized distributors?

All ZTX550STOA 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 ZTX550STOA meets industry standards.

7.What is the process for return or replacement of ZTX550STOA?

All ZTX550STOA units undergo pre-shipment inspection (PSI). If there is an issue with ZTX550STOA, 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 ZTX550STOA part is unused and in its original packaging.

Return procedure for ZTX550STOA:

1.Submit a request within 90 days.

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

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