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

Diodes Incorporated ZTX550STOB

Name: ZTX550STOB
Brand: Diodes Incorporated
SKU: ZTX550STOB
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: ZTX550STOB

Manufacturer:: Diodes Incorporated

Category:: Single Bipolar Transistors

Package:: E-Line-3, Formed Leads

Datasheet:: ZTX550STOB.pdf

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

Quantity:: RFQ Add To RFQ list

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Inventory:8,326

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Product details

Overview

ZTX550STOB from Diodes Incorporated is an 80V PNP medium-power transistor in E-Line (TO-92 compatible) package, rated for -1A continuous collector current, -2A peak pulse current, and 1W power dissipation at +25°C ambient. It operates up to +200°C junction temperature and is RoHS-compliant, halogen-free, and qualified to JEDEC high-reliability standards. It serves as a switching or linear amplifier in DC-DC converters and LCD backlight circuits.

For engineers reviewing the ZTX550STOB datasheet, ZTX550STOB pinout, ZTX550STOB application, or ZTX550STOB equivalent, key selection criteria include its -65V V_CEO, -1.1V V_BE(sat) at -150mA/-15mA, h_FE range of 50–150 at -1A, f_T = 150MHz, and thermal resistance R_θJA = 175°C/W under minimum pad layout conditions.

Technical Context

The ZTX550STOB is a silicon PNP bipolar junction transistor optimized for medium-power switching and linear amplification in industrial and automotive-qualified systems. Its design emphasizes high-voltage blocking (-80V V_CBO), robust thermal performance (T_J up to +200°C), and stable gain across current ranges.

It features a low-saturation voltage (-350mV V_CE(sat) at -150mA/-15mA), moderate current gain bandwidth (f_T = 150MHz), and JEDEC-classified ESD protection (4kV HBM). The device is not AEC-Q101 qualified by default but supports automotive-grade variants (e.g., ZTX551Q) with PPAP capability and IATF 16949 manufacturing.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	-65 V - Maximum safe collector-emitter voltage before breakdown under open-base condition
I_C	-1 A - Continuous DC collector current rating defining steady-state power handling
P_D	1 W - Max power dissipation on standard PCB layout; limits thermal rise without heatsink
h_FE	50–150 - DC current gain range at -1A/-10V, critical for base drive sizing in switch designs
f_T	150 MHz - Transition frequency indicating usable bandwidth for RF or fast-switching applications
R_θJA	175 °C/W - Thermal resistance from junction to ambient on minimal pad layout; determines ΔT_J rise per watt
T_J max	+200 °C - Maximum allowable junction temperature enabling operation in high-ambient environments

Pinout & Package

Package: E-Line (TO-92 compatible molded plastic package, UL 94V-0 rated, matte tin-plated leads, 0.159g weight).

Pin/Terminal	Circuit Role	Design Meaning
Emitter (E)	Current sink terminal for PNP operation	Connected to higher potential rail; base-emitter forward bias initiates conduction
Collector (C)	Main current output path	Carries load current to ground; voltage swing limited by -65V V_CEO rating
Base (B)	Control input for transistor turn-on/turn-off	Requires ~-1.1V V_BE(sat) at -150mA drive; controls h_FE-dependent collector current

Key Features

Feature	Design Value
High-voltage PNP structure	Rated for -80V V_CBO and -65V V_CEO, supporting 48V+ industrial bus switching
Thermal resilience	Specified for +200°C maximum junction temperature, enabling use in engine bay or enclosed power modules
Green compliance	Fully RoHS 3 compliant, halogen- and antimony-free (<900ppm Br/Cl, <1000ppm Sb), meeting automotive Tier-1 material requirements
ESD robustness	4kV HBM rating per JEDEC JESD22-A114, reducing handling sensitivity during assembly

Applications

LCD Backlight Converters

Emergency Lighting Drivers

Use Scenario: Step-up DC-DC converter driving CCFL or LED strings in automotive instrument clusters.

IC Role / Device Role / Timing Role: PNP switch controlling primary-side current in flyback or boost topology.

Use Value: -65V V_CEO withstands reflected voltage spikes; 1W PD supports 100–200mA output without forced cooling.

Use Scenario: Battery-backed constant-current driver for LED exit signs in commercial buildings.

IC Role / Device Role / Timing Role: Linear or PWM-controlled pass transistor regulating LED current during mains failure.

Use Value: Stable h_FE over -55°C to +125°C ambient ensures consistent dimming control across temperature extremes.

Industrial DC-DC Modules

Automotive HVAC Blower Controls

Use Scenario: Isolated auxiliary supply in PLC I/O modules converting 24V to 5V/3.3V.

IC Role / Device Role / Timing Role: Medium-power PNP switch in secondary-side synchronous rectifier or linear post-regulator.

Use Value: 150MHz f_T enables clean switching at 100–500kHz, minimizing gate drive losses in discrete driver stages.

Use Scenario: Low-side current limiter in brushed DC motor control for cabin air circulation fans.

IC Role / Device Role / Timing Role: High-temp PNP transistor in current-sense feedback loop or motor enable stage.

Use Value: +200°C T_J rating allows placement near hot motor housings without derating or thermal shutdown.

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; improved -65V V_CEO (vs. -45V for ZTX550), higher h_FE min (50 vs. 100 at -150mA), released status	Direct replacement where higher voltage margin and gain consistency are required	Select ZTX551 for new designs; ZTX550STOB is obsolete per Diodes' ordering guide
MJD2955	TO-220 package; -60V V_CEO, -10A I_C, 15W P_D; larger footprint and higher thermal mass	Suitable for higher-current, lower-frequency linear regulation where PCB space permits	Choose only if >1A continuous current or heatsink-mounting is needed; not drop-in compatible

Compared with ZTX550STOB, ZTX551 offers verified production status and tighter gain spec at full load, while MJD2955 trades compactness for higher power handling-neither matches the exact thermal profile or lead-form of the E-Line package.

Availability

ZTX550STOB is available at Aetrix Electronics and suitable for LCD backlight converters, emergency lighting drivers, and industrial DC-DC modules requiring stable component supply and legacy design continuity.

Supply support for ZTX550STOB 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 North America.

The ZTX series targets medium-power bipolar transistors for industrial, automotive, and consumer power conversion, emphasizing high-voltage capability, thermal reliability, and green compliance in through-hole packages.

FAQ

Is ZTX550STOB still in active production?

No. According to Diodes Incorporated's official ordering information, ZTX550 (including STOB variant) is marked "Obsolete (Use ZTX551)". ZTX551 is the released, functionally enhanced successor with identical E-Line packaging and improved V_CEO and h_FE specifications.

What is the correct pinout orientation for ZTX550STOB in E-Line package?

Viewing the flat face with the ejection mark at the bottom, pins from left to right are Emitter (E), Collector (C), Base (B). This matches the standardized E-Line TO-92-compatible configuration confirmed in DS33273 Rev. 2–2 Figure 1 and mechanical drawings.

Can ZTX550STOB be used in automotive applications?

ZTX550STOB itself is not AEC-Q101 qualified. However, Diodes offers automotive-grade versions (e.g., ZTX551Q) manufactured in IATF 16949 facilities, PPAP-capable, and qualified to AEC-Q101. For automotive use, ZTX551Q-not ZTX550STOB-is the designated qualified part.

What is the maximum safe operating frequency for ZTX550STOB in switching mode?

With f_T = 150MHz, ZTX550STOB supports reliable switching up to ~10–20MHz in optimized layouts. Practical hard-switching applications (e.g., DC-DC converters) typically operate ≤500kHz to maintain acceptable V_CE(sat) and thermal stability, per its 1W power limit and R_θJA = 175°C/W rating.

ZTX550STOB 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)

ZTX550STOB FAQ

1.How can I place an order for ZTX550STOB through Aetrix?

Please submit a Request for Quotation (RFQ) for ZTX550STOB 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 ZTX550STOB reliable?

The price and inventory of ZTX550STOB are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for ZTX550STOB is usually 5 days.

3.What payment methods are accepted for ZTX550STOB?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for ZTX550STOB transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for ZTX550STOB?

ZTX550STOB orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your ZTX550STOB 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 ZTX550STOB?

For technical support, including ZTX550STOB datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your ZTX550STOB requirements.

6.How does Aetrix verify that ZTX550STOB is sourced from the original manufacturer or authorized distributors?

All ZTX550STOB 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 ZTX550STOB meets industry standards.

7.What is the process for return or replacement of ZTX550STOB?

All ZTX550STOB units undergo pre-shipment inspection (PSI). If there is an issue with ZTX550STOB, 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 ZTX550STOB part is unused and in its original packaging.

Return procedure for ZTX550STOB:

1.Submit a request within 90 days.

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

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