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

Diodes Incorporated ZTX618STOB

Name: ZTX618STOB
Brand: Diodes Incorporated
SKU: ZTX618STOB
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: ZTX618STOB

Manufacturer:: Diodes Incorporated

Category:: Single Bipolar Transistors

Package:: E-Line-3, Formed Leads

Datasheet:: ZTX618STOB.pdf

Description:: TRANS NPN 20V 3.5A E-LINE

Quantity:: RFQ Add To RFQ list

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Inventory:4,395

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Product details

Overview

ZTX618STOB from Diodes Incorporated (formerly Zetex) is an NPN silicon planar medium-power high-gain transistor designed for switching and linear amplification in power control circuits, with confirmed V_CEO = 20 V, I_C = 3.5 A continuous, h_FE ≥ 200 at I_C = 10 mA, V_CE(sat) = 7 mV typ. at I_C = 0.1 A / I_B = 10 mA, and TO-92 compatible E-Line package - widely used in MOSFET gate driver stages.

For engineers reviewing the ZTX618STOB datasheet, ZTX618STOB pinout, ZTX618STOB application, or ZTX618STOB equivalent, key selection criteria include pulsed current capability (I_CM = 10 A), low saturation voltage under high drive conditions, thermal resistance (R_th(j-amb) = 116 °C/W on 1 in² PCB copper), and h_FE stability across I_C = 10 mA to 10 A.

Technical Context

This NPN bipolar junction transistor operates in active, saturation, and cutoff regions with verified DC current gain (h_FE) ranging from 40–450 depending on collector current (10 mA to 10 A) and V_CE = 2 V. Its low V_CE(sat) (7–255 mV) and fast switching (t_on = 170 ns, t_off = 400 ns) support efficient gate driving of power MOSFETs in pulsed-load applications.

The device features a maximum junction temperature of +200 °C and thermal resistance of 116 °C/W when mounted on ≥1 in² PCB copper, enabling reliable operation in thermally constrained industrial power stages without forced cooling.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	20 V - Maximum safe collector-emitter voltage before breakdown under open-base condition.
I_C (cont)	3.5 A - Continuous DC collector current rating defining steady-state power stage capacity.
V_CE(sat)	7 mV typ. at I_C = 0.1 A / I_B = 10 mA - Enables minimal conduction loss in low-voltage switching nodes.
h_FE	200–450 - Confirmed DC current gain range supporting stable base drive design across 10 mA–10 A load currents.
f_T	100–140 MHz - Transition frequency confirming suitability for high-speed switching up to ~10 MHz practical operation.
R_th(j-amb)	116 °C/W - Thermal resistance on 1 in² PCB copper, defining required board layout for thermal management.

Pinout & Package

Package: TO-92 compatible E-Line (3-lead plastic package with emitter-collector-base pin order matching standard TO-92 footprint).

Pin/Terminal	Circuit Role	Design Meaning
E (Emitter)	Current sink terminal	Reference node for base drive return path; connects to ground or low-side reference in gate driver configurations.
C (Collector)	Current source terminal	Drives MOSFET gate through series resistor; must withstand V_CEO = 20 V and I_CM = 10 A peak.
B (Base)	Control input terminal	Accepts TTL/CMOS-compatible logic-level drive; requires I_B ≤ 500 mA max per absolute ratings.

Key Features

Feature	Design Value
Low V_CE(sat)	7 mV typical at light load - reduces power dissipation and improves efficiency in gate drive output stage.
High pulsed current	10 A peak - supports transient gate charge delivery for fast-turn-on of large MOSFETs.
Wide h_FE range	40–450 across 10 mA–10 A - enables predictable base drive sizing over full operating current span.
High T_j rating	+200 °C max junction temperature - allows operation in high-ambient industrial environments without derating.

Applications

Power MOSFET Gate Driver

DC-DC Converter Switching Stage

Use Scenario: Driving the gate of high-current N-channel MOSFETs in half-bridge or synchronous buck converters.

IC Role / Device Role / Timing Role: NPN switch providing low-impedance pull-down path and controlled turn-on via base current.

Use Value: 7 mV V_CE(sat) minimizes conduction loss during MOSFET on-state; 10 A pulse rating handles gate charge surge.

Use Scenario: Active clamping or auxiliary switching in isolated flyback or forward converter topologies.

IC Role / Device Role / Timing Role: Medium-power switching transistor handling primary-side snubbing or bias winding regulation.

Use Value: 20 V V_CEO and 3.5 A I_C support safe operation across common 12–19 V bias rails with margin.

Industrial Motor Control Interface

Overcurrent Protection Circuit

Use Scenario: Level-shifting and isolation interface between microcontroller GPIO and IGBT/MOSFET gate drivers in BLDC controllers.

IC Role / Device Role / Timing Role: Signal-level translator and current amplifier ensuring robust gate drive under EMI-prone motor noise.

Use Value: High h_FE (≥200 at 10 mA) guarantees sufficient base current gain for logic-level input compatibility.

Use Scenario: Fast-acting current-sense switch triggering shutdown in battery protection ICs or power supply foldback circuits.

IC Role / Device Role / Timing Role: Precision current-triggered switch with sub-200 ns turn-on time for fault response.

Use Value: 170 ns t_on and 400 ns t_off enable <1 µs total response - critical for lithium-cell overcurrent cutoff.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
ZTX653STOB	V_CEO = 60 V, I_C = 3 A, higher V_CE(sat) (150 mV typ. at 1 A)	Better voltage headroom but lower current and higher saturation loss	Select when >20 V bus voltage or enhanced avalanche margin is required.
MPSA42	V_CEO = 300 V, I_C = 500 mA, f_T = 50 MHz - optimized for HV, not high-current drive	Unsuitable for 3.5 A continuous or 10 A pulse gate drive	Only consider for high-voltage, low-current signal switching where ZTX618STOB's current capability is unnecessary.

Compared with ZTX618STOB, ZTX653STOB trades current capability and low saturation for higher voltage rating, while MPSA42 offers no meaningful functional overlap in gate-driving applications due to its 0.5 A current limit and 5× slower switching.

Availability

ZTX618STOB is available at Aetrix Electronics and suitable for power MOSFET gate drivers, DC-DC converter switching stages, industrial motor control interfaces, and overcurrent protection circuits requiring stable component supply and long-term industrial lifecycle support.

Supply support for ZTX618STOB 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 acquired Zetex plc in 2008 and maintains its legacy high-performance discrete portfolio, emphasizing reliability, thermal robustness, and application-specific optimization for industrial and automotive markets.

The ZTX series targets medium-power bipolar switching applications where low saturation voltage, high pulsed current, and wide h_FE stability are essential - particularly in gate driver, power conversion, and protection circuitry.

FAQ

What is the maximum safe base current for ZTX618STOB?

The absolute maximum base current is 500 mA, as specified in the Absolute Maximum Ratings table. Exceeding this risks metallization failure or bond wire damage. For reliable operation, design base drive to deliver ≤50 mA under normal 3.5 A collector load (IC/IB = 70), reserving headroom for transient peaks.

Can ZTX618STOB be used in linear amplifier applications?

Yes - its h_FE stability (200–450) and low V_CE(sat) support Class-A and AB amplifier stages up to ~1 W output. However, thermal derating must be applied: P_tot drops from 1 W at 25°C to 0.25 W at 125°C ambient, requiring heatsinking for sustained linear use above 100 mA collector current.

Is ZTX618STOB RoHS compliant and lead-free?

Yes - Diodes Incorporated confirms ZTX618STOB is manufactured in full compliance with RoHS Directive 2011/65/EU and REACH Regulation (EC) No. 1907/2006. The TO-92 package uses lead-free matte tin plating on external terminations, with no exemptions claimed.

How does PCB copper area affect ZTX618STOB's power handling?

Thermal resistance R_th(j-amb) is 116 °C/W with ≥1 in² copper; reducing copper to 0.25 in² increases it to ~175 °C/W. At 3.5 A and V_CE(sat) = 150 mV, power dissipation is 0.525 W - resulting in ~61 °C junction rise on minimal copper vs. ~41 °C on full copper, directly impacting safe continuous operation.

ZTX618STOB 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

Current - Collector (Ic) (Max):: 3.5 A

Voltage - Collector Emitter Breakdown (Max):: 20 V

Vce Saturation (Max) @ Ib, Ic:: 255mV @ 50mA, 3.5A

Current - Collector Cutoff (Max):: 100nA

DC Current Gain (hFE) (Min) @ Ic, Vce:: 300 @ 200mA, 2V

Power - Max:: 1 W

Frequency - Transition:: 140MHz

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

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

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

ZTX618STOB FAQ

1.How can I place an order for ZTX618STOB through Aetrix?

Please submit a Request for Quotation (RFQ) for ZTX618STOB 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 ZTX618STOB reliable?

The price and inventory of ZTX618STOB are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for ZTX618STOB is usually 5 days.

3.What payment methods are accepted for ZTX618STOB?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for ZTX618STOB transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for ZTX618STOB?

ZTX618STOB orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your ZTX618STOB 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 ZTX618STOB?

For technical support, including ZTX618STOB datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your ZTX618STOB requirements.

6.How does Aetrix verify that ZTX618STOB is sourced from the original manufacturer or authorized distributors?

All ZTX618STOB 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 ZTX618STOB meets industry standards.

7.What is the process for return or replacement of ZTX618STOB?

All ZTX618STOB units undergo pre-shipment inspection (PSI). If there is an issue with ZTX618STOB, 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 ZTX618STOB part is unused and in its original packaging.

Return procedure for ZTX618STOB:

1.Submit a request within 90 days.

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

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