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

Diodes Incorporated ZTX603STOA

Name: ZTX603STOA
Brand: Diodes Incorporated
SKU: ZTX603STOA
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: ZTX603STOA

Manufacturer:: Diodes Incorporated

Category:: Single Bipolar Transistors

Package:: E-Line-3, Formed Leads

Datasheet:: ZTX603STOA.pdf

Description:: TRANS NPN DARL 80V 1A E-LINE

Quantity:: RFQ Add To RFQ list

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Inventory:7,161

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Product details

Overview

ZTX603STOA from Diodes Incorporated is an NPN silicon planar medium-power Darlington transistor with V_CEO = 80 V, I_C = 1 A continuous, h_FE ≥ 2000 at I_C = 1 A, P_tot = 1 W at T_amb = 25°C, and TO-92 compatible package - used in linear power regulation, relay drivers, and low-frequency switching in industrial control modules.

For engineers reviewing the ZTX603STOA datasheet, ZTX603STOA pinout, ZTX603STOA application, or ZTX603STOA equivalent, key selection criteria include verified Darlington gain stability at 1 A, V_CE(sat) ≤ 1.0 V under I_C/I_B = 1000, thermal derating behavior above 25°C, and E-line TO-92 mechanical compatibility with legacy board layouts.

Technical Context

This Darlington pair integrates two NPN transistors in cascade to achieve high DC current gain while maintaining single-package simplicity. It operates with base-emitter turn-on voltage V_BE(on) = 1.7 V at I_C = 1 A and V_CE = 5 V, and exhibits typical transition frequency f_T = 150 MHz at I_C = 100 mA, V_CE = 10 V - suitable for low-speed switching but not RF amplification.

Thermal design requires attention: maximum ambient temperature is governed by the derating equation T_amb(max) = (P_max − P_act) / 0.0057 + 25°C, where P_max depends on V_CE and source resistance R_S, per the published voltage derating graph.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	80 V - maximum collector-emitter voltage before breakdown under open-base conditions; defines safe operating voltage headroom in relay driver circuits.
I_C (continuous)	1 A - rated DC collector current; supports driving 12 V/500 mA solenoids or small DC motors without external heat sinking at 25°C.
h_FE	≥2000 at I_C = 1 A - high Darlington gain enables microcontroller GPIO-level base drive (e.g., 1 mA base current switches 1 A load).
V_CE(sat)	≤1.0 V at I_C = 1 A, I_B = 1 mA - low saturation voltage minimizes conduction loss and self-heating in linear regulator or lamp dimmer applications.
P_tot	1 W at T_amb = 25°C - total power dissipation limit; derates linearly at 5.7 mW/°C above 25°C, requiring thermal margin planning for enclosure designs.
f_T	150 MHz - transition frequency measured at I_C = 100 mA; confirms usable bandwidth for <100 kHz switching but not for fast digital logic interfacing.
V_BE(sat)	1.8 V at I_C = 1 A, I_B = 1 mA - elevated base-emitter saturation voltage reflects Darlington architecture; impacts minimum drive voltage requirements.

Pinout & Package

Supplied in E-line TO-92 compatible package (3-lead plastic case), with standard C-B-E terminal arrangement matching legacy ZTX60x series footprints. Lead finish is matte tin, RoHS-compliant.

Pin/Terminal	Circuit Role	Design Meaning
Collector (C)	Main current output node	Connected to load high-side; must withstand up to 80 V transient spikes in inductive switching applications.
Base (B)	Control input for Darlington pair	Receives low-current drive (e.g., MCU GPIO); internal resistor-free design requires external current-limiting resistor.
Emitter (E)	Common emitter reference	Returned to system ground or negative rail; carries full load current and sets V_BE bias point for gain stability.

Key Features

Feature	Design Value
Darlington configuration	Two cascaded NPN transistors in one die - delivers >2000 h_FE at 1 A without external feedback components.
TO-92 mechanical compatibility	E-line footprint matches ZTX602/ZTX603 legacy boards - enables drop-in replacement without PCB redesign.
High V_CEO rating	80 V collector-emitter breakdown - supports 24 V industrial control rails with 3× safety margin against inductive kickback.
Low V_CE(sat)	≤1.0 V at full 1 A load - reduces power loss to ≤1 W, simplifying thermal management in space-constrained enclosures.

Applications

Relay Driver Circuit

Linear Voltage Regulator

Use Scenario: Driving 12 V, 400 mA electromagnetic relays in PLC I/O modules with 3.3 V or 5 V microcontroller outputs.

IC Role / Device Role / Timing Role: High-gain Darlington switch providing galvanic isolation between logic and load, with built-in current gain staging.

Use Value: Eliminates need for discrete two-transistor stages; V_CE(sat) ≤ 1.0 V ensures relay coil energizes fully even with marginal supply voltage.

Use Scenario: Pass element in adjustable 5–15 V, 500 mA linear regulators for analog sensor signal conditioning circuits.

IC Role / Device Role / Timing Role: Series pass transistor regulating output voltage via base bias control from error amplifier feedback loop.

Use Value: High h_FE allows precise current mirroring and stable regulation with minimal base drive current variation.

Lamp Dimmer Module

DC Motor Speed Control

Use Scenario: Phase-angle or PWM-controlled incandescent lamp dimming in building automation panels.

IC Role / Device Role / Timing Role: Medium-power switching element handling 1 A RMS lamp current at 50/60 Hz line frequency.

Use Value: 80 V V_CEO accommodates peak AC line voltages (e.g., 230 V_RMS ≈ 325 V_peak) when used with snubber networks.

Use Scenario: Unidirectional speed control of 12 V, 800 mA brushed DC motors in HVAC damper actuators.

IC Role / Device Role / Timing Role: Low-frequency PWM switch controlling average motor voltage via duty-cycle modulation.

Use Value: Verified 1.1 µs typical turn-off time supports PWM frequencies up to 10 kHz without excessive switching loss.

Equivalent & Alternatives

The following parts are listed as comparable options for similar Darlington transistor applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
ZTX602STOA	V_CEO = 60 V (vs. 80 V); otherwise identical pinout, gain, and saturation specs.	Not suitable for 24 V systems with transient overvoltage risk; limited to ≤12 V relay/motor loads.	Select only if operating voltage stays below 40 V peak and thermal budget permits same derating curve.
BC817-40,215	Single NPN (not Darlington); h_FE = 250–630; V_CEO = 45 V; SOT-23 package.	Cannot replace ZTX603STOA directly - requires external gain-boosting stage and cannot handle 1 A continuously.	Use only in low-current (<100 mA), surface-mount designs where Darlington functionality is not required.

Compared with ZTX602STOA, the ZTX603STOA provides 20 V higher V_CEO headroom critical for 24 V industrial systems; versus BC817-40, it delivers integrated Darlington gain and through-hole TO-92 mounting essential for high-current, serviceable designs.

Availability

ZTX603STOA is available at Aetrix Electronics and suitable for relay driver circuits, linear voltage regulators, lamp dimmer modules, and DC motor speed control applications requiring stable component supply across extended production lifecycles.

Supply support for ZTX603STOA 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 semiconductor company specializing in discrete, analog, and mixed-signal ICs for industrial, computing, consumer, and communications markets.

The ZTX603STOA belongs to the ZTX60x series of medium-power Darlington transistors designed specifically for cost-sensitive, high-reliability linear and switching applications in industrial controls and power interface modules.

FAQ

What is the maximum safe continuous collector current for ZTX603STOA at 70°C ambient?

At T_amb = 70°C, derating applies: 5.7 mW/°C × (70 − 25) = 256.5 mW reduction from 1 W → P_tot = 743.5 mW. Using V_CE(sat) = 1.0 V, max I_C = P_tot/V_CE(sat) ≈ 0.74 A. This assumes no additional heatsinking and still within SOA limits per the published Safe Operating Area graph.

Can ZTX603STOA be used in avalanche mode for energy clamping?

No - ZTX603STOA is not characterized or rated for controlled avalanche operation. Its V_(BR)CEO = 80 V is a breakdown limit, not a designed clamping voltage. For inductive load protection, external TVS diodes or RC snubbers are required per application notes in Diodes Inc.'s ZTX60x datasheet.

Is the base-emitter junction protected against reverse voltage?

No internal protection is provided. The absolute maximum V_EBO is 10 V, and reverse base-emitter voltage must be limited to ≤8 V (per I_EBO test condition). In bidirectional drive or inductive flyback scenarios, an external anti-parallel diode across B–E is recommended to prevent junction damage.

Does ZTX603STOA have a built-in base resistor?

No - ZTX603STOA is a bare Darlington transistor with no integrated base resistor. External base current limiting is mandatory; typical design uses a 4.7 kΩ resistor from 5 V MCU GPIO to ensure I_B ≈ 1 mA at V_BE(on) ≈ 1.7 V, enabling full 1 A collector drive with h_FE ≥ 2000.

ZTX603STOA 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:: NPN - Darlington

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

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

Vce Saturation (Max) @ Ib, Ic:: 1V @ 1mA, 1A

Current - Collector Cutoff (Max):: 10µA

DC Current Gain (hFE) (Min) @ Ic, Vce:: 2000 @ 1A, 5V

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)

ZTX603STOA FAQ

1.How can I place an order for ZTX603STOA through Aetrix?

Please submit a Request for Quotation (RFQ) for ZTX603STOA 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 ZTX603STOA reliable?

The price and inventory of ZTX603STOA are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for ZTX603STOA is usually 5 days.

3.What payment methods are accepted for ZTX603STOA?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for ZTX603STOA transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for ZTX603STOA?

ZTX603STOA orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your ZTX603STOA 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 ZTX603STOA?

For technical support, including ZTX603STOA datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your ZTX603STOA requirements.

6.How does Aetrix verify that ZTX603STOA is sourced from the original manufacturer or authorized distributors?

All ZTX603STOA 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 ZTX603STOA meets industry standards.

7.What is the process for return or replacement of ZTX603STOA?

All ZTX603STOA units undergo pre-shipment inspection (PSI). If there is an issue with ZTX603STOA, 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 ZTX603STOA part is unused and in its original packaging.

Return procedure for ZTX603STOA:

1.Submit a request within 90 days.

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

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