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

Diodes Incorporated ZTX455QSTZ

Name: ZTX455QSTZ
Brand: Diodes Incorporated
SKU: ZTX455QSTZ
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: ZTX455QSTZ

Manufacturer:: Diodes Incorporated

Category:: Single Bipolar Transistors

Package:: E-Line-3, Formed Leads

Datasheet:: ZTX455QSTZ.pdf

Description:: TRANS NPN 140V 1A E-LINE

Quantity:: RFQ Add To RFQ list

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Inventory:5,922

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Product details

Overview

ZTX455QSTZ from Diodes Incorporated is an NPN silicon planar medium-power transistor designed for switching and linear amplification in industrial control, power supply regulation, and relay driver circuits. It features 140 V V_CEO, 1 A continuous collector current, 1 W power dissipation at 25°C, and a minimum h_FE of 100 at I_C = 150 mA / V_CE = 10 V - enabling robust signal gain and reliable saturation in 24 V DC control stages.

For engineers reviewing the ZTX455QSTZ datasheet, ZTX455QSTZ pinout, ZTX455QSTZ application, or ZTX455QSTZ equivalent, key selection criteria include verified V_CEO(sus) = 140 V, guaranteed h_FE ≥ 100 under linear bias, f_T = 100 MHz at 50 mA, C_obo = 15 pF, and TO-92-compatible mechanical footprint for legacy board compatibility.

Technical Context

This transistor operates as a general-purpose NPN switch/amplifier with fixed-emitter bias topology. Its 140 V V_CEO(sus) rating supports operation in 24–48 V industrial bus systems, while the 100 MHz f_T enables stable performance up to audio-frequency switching (e.g., PWM-driven solenoid drivers). The 15 pF C_obo and low V_CE(sat) (0.7 V @ I_C = 200 mA / I_B = 20 mA) reduce switching losses and improve turn-off speed.

Thermal design is constrained by its 1 W P_tot at T_amb = 25°C and -55°C to +200°C operating junction range. The device exhibits typical safe operating area (SOA) compliance up to 100 µs pulses at 1 A, making it suitable for non-repetitive surge handling in protection circuits without external snubbers.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	140 V - Sustains 140 V collector-emitter voltage before breakdown; enables use in 48 V rail switching with 3× safety margin.
I_C (continuous)	1 A - Supports steady-state load currents up to 1 A; sufficient for driving 12 V/24 V relays or small motors.
P_tot	1 W at T_amb = 25°C - Limits thermal derating above ambient; requires heatsinking above ~60°C ambient.
h_FE	100–300 - Provides predictable current gain across 150 mA–1 A range; ensures stable base drive sizing in discrete amplifier stages.
f_T	100 MHz - Enables reliable operation up to ~10 MHz square-wave switching; suitable for audio-range PWM and signal buffering.
C_obo	15 pF - Low output capacitance minimizes Miller effect; improves high-frequency stability in common-emitter configurations.

Pinout & Package

Supplied in a TO-92 compatible through-hole package with standard E-Line pin assignment: Emitter (pin 1), Base (pin 2), Collector (pin 3).

Pin/Terminal	Circuit Role	Design Meaning
Pin 1 (Emitter)	Current sink terminal	Connected to ground or low-side return path; defines reference for V_BE bias and current sensing.
Pin 2 (Base)	Control input	Receives forward-biased current to enable conduction; requires series resistor to limit I_B per h_FE target.
Pin 3 (Collector)	High-side switched node	Connects to load and supply rail; carries full I_C; must be isolated from PCB copper pour if dissipating >0.5 W.

Key Features

Feature	Design Value
High V_CEO(sus)	140 V sustains transient overvoltage in 24 V industrial buses without clamping diodes.
Guaranteed h_FE min	100 at I_C = 150 mA ensures predictable base drive requirements across production lots.
Low V_CE(sat)	0.7 V @ I_C = 200 mA / I_B = 20 mA reduces conduction loss and self-heating in continuous switching.
TO-92 compatibility	E-Line pinout matches legacy ZTX450-series footprints, enabling drop-in replacement on existing PCBs.

Applications

Industrial Relay Driver

DC-DC Converter Switch

Use Scenario: Driving 24 V, 500 mA coil relays in PLC I/O modules with microcontroller GPIO control.

IC Role / Device Role / Timing Role: NPN switch providing galvanic isolation between logic-level MCU and inductive load.

Use Value: 140 V V_CEO absorbs flyback spikes up to 120 V without external suppression; 1 A I_C headroom prevents thermal runaway during relay pull-in.

Use Scenario: Low-cost main switch in 5–12 V input, 3.3 V/1 A buck converter for embedded sensor nodes.

IC Role / Device Role / Timing Role: Pulse-width modulated power switch operating at ≤ 100 kHz with fixed duty cycle.

Use Value: 100 MHz f_T and 15 pF C_obo ensure clean turn-on/turn-off edges; 0.7 V V_CE(sat) limits conduction loss to < 0.14 W at 200 mA.

Linear Voltage Regulator Pass Element

Overvoltage Protection Circuit

Use Scenario: Series pass transistor in adjustable 3–15 V linear regulator supplying analog front-end circuitry.

IC Role / Device Role / Timing Role: Continuously biased active element regulating output via emitter-follower configuration.

Use Value: h_FE ≥ 100 ensures stable loop gain; 1 W P_tot allows 1.5 W peak dissipation for short transients with adequate heatsinking.

Use Scenario: Crowbar device triggered by Zener reference to clamp 48 V supply rail during overvoltage events.

IC Role / Device Role / Timing Role: Fast-acting shunt switch activated by gate-controlled base bias to short rail to ground.

Use Value: 140 V V_CEO(sus) withstands pre-clamp surges; 2 A I_CM handles 100 µs fault currents without second breakdown.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
ZTX450	V_CEO = 120 V; h_FE min = 30 @ I_C = 1 A	Lower voltage rating limits use in 48 V systems; reduced gain increases base drive burden.	Select only where V_in ≤ 36 V and base current budget permits higher I_B.
MPSA42	V_CEO = 300 V; h_FE = 40–250; TO-92 but different pinout (C-B-E)	Higher voltage capability trades off lower h_FE consistency and non-compatible pin mapping.	Use when >200 V blocking required; verify PCB layout for reversed collector/emitter pins.

Compared with ZTX450 and MPSA42, ZTX455QSTZ delivers optimal balance of 140 V ruggedness, 100+ h_FE linearity, and TO-92 E-Line pinout - making it preferred for 24–48 V industrial switching where gain predictability and layout continuity matter.

Availability

ZTX455QSTZ is available at Aetrix Electronics and suitable for industrial relay drivers, DC-DC converter switches, linear voltage regulator pass elements, and overvoltage protection circuits requiring stable component supply across long-lifecycle manufacturing programs.

Supply support for ZTX455QSTZ 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 centers across Asia and Europe.

ZTX455QSTZ belongs to the ZTX series of general-purpose bipolar transistors engineered for industrial-grade reliability, wide temperature operation (-55°C to +200°C), and compatibility with legacy through-hole assembly processes.

FAQ

Is ZTX455QSTZ RoHS compliant?

Yes, ZTX455QSTZ meets RoHS Directive 2011/65/EU and is lead-free with matte tin lead finish. The device complies with JEDEC J-STD-020 moisture sensitivity level (MSL) 1 and has no halogenated flame retardants in its epoxy molding compound.

What is the maximum safe pulsed collector current?

The absolute maximum pulsed collector current (I_CM) is 2 A, specified under pulse conditions: 300 µs width, ≤2% duty cycle, and T_amb = 25°C. Exceeding these parameters risks secondary breakdown or bond wire fusing.

Can ZTX455QSTZ replace ZTX454 in existing designs?

Yes, ZTX455QSTZ is a direct upgrade to ZTX454 with identical TO-92 E-Line pinout and improved specs: V_CEO increased from 120 V to 140 V and h_FE minimum raised from 30 to 100 at I_C = 150 mA - no layout or bias changes required.

Does ZTX455QSTZ require a heatsink in 1 A continuous operation?

At 1 A and V_CE(sat) ≈ 0.9 V, power dissipation reaches ~0.9 W. With θ_JA ≈ 200°C/W for TO-92 on 1 sq-in FR4, junction temperature exceeds 200°C. A minimal copper pad (≥0.5 sq-in) or clip-on heatsink is required for sustained 1 A operation.

ZTX455QSTZ Specifications

Product attributes: Attribute value

Manufacturer:: Diodes Incorporated

Series:: -

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

Packaging:: Tape & Box (TB)

Product Status:: Obsolete

Transistor Type:: NPN

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

Voltage - Collector Emitter Breakdown (Max):: 140 V

Vce Saturation (Max) @ Ib, Ic:: 700mV @ 15mA, 150mA

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

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

Power - Max:: 1 W

Frequency - Transition:: 100MHz

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

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

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

ZTX455QSTZ FAQ

1.How can I place an order for ZTX455QSTZ through Aetrix?

Please submit a Request for Quotation (RFQ) for ZTX455QSTZ 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 ZTX455QSTZ reliable?

The price and inventory of ZTX455QSTZ are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for ZTX455QSTZ is usually 5 days.

3.What payment methods are accepted for ZTX455QSTZ?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for ZTX455QSTZ transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for ZTX455QSTZ?

ZTX455QSTZ orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your ZTX455QSTZ 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 ZTX455QSTZ?

For technical support, including ZTX455QSTZ datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your ZTX455QSTZ requirements.

6.How does Aetrix verify that ZTX455QSTZ is sourced from the original manufacturer or authorized distributors?

All ZTX455QSTZ 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 ZTX455QSTZ meets industry standards.

7.What is the process for return or replacement of ZTX455QSTZ?

All ZTX455QSTZ units undergo pre-shipment inspection (PSI). If there is an issue with ZTX455QSTZ, 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 ZTX455QSTZ part is unused and in its original packaging.

Return procedure for ZTX455QSTZ:

1.Submit a request within 90 days.

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

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