Diodes Incorporated ZTX618

Overview

ZTX618 from Diodes Incorporated (formerly Zetex plc) is an NPN silicon planar medium-power high-gain transistor designed for switching and linear amplification in power control circuits, especially as a gate driver for power MOSFETs. It delivers 3.5 A continuous collector current, 10 A peak pulse current, and exhibits low V_CE(sat) of 7 mV (typ.) at IC = 0.1 A / IB = 10 mA, with h_FE up to 450 at IC = 10 A.

For engineers reviewing the ZTX618 datasheet, ZTX618 pinout, ZTX618 application, or ZTX618 equivalent, key selection criteria include its TO-92-compatible E-Line package, safe operating area at high pulse currents, low saturation voltage for minimal conduction loss, and thermal resistance of 116 °C/W when mounted on 1 sq. in. PCB copper.

Technical Context

The ZTX618 operates as a medium-power bipolar junction transistor with planar epitaxial construction, optimized for high-current switching where low V_CE(sat) and robust h_FE linearity up to 10 A are critical. Its breakdown ratings-V_CEO = 20 V, V_CBO = 20 V, and V_EBO = 5 V-define its use in low-voltage, high-current drive stages.

Thermal performance is specified with two R_th(j–amb) values (175 °C/W free-air, 116 °C/W on 1 sq. in. copper), confirming its reliance on PCB copper for thermal management. Transition frequency f_T = 100–140 MHz at IC = 50 mA supports fast switching, while turn-on/turn-off times of 170 ns / 400 ns (V_CC = 10 V, I_C = 1 A) validate suitability for MOSFET gate driving.

Key Specifications

Pinout & Package

Package: TO-92-compatible E-Line (3-lead, straight lead form, epoxy molded). Standard pinout orientation (flat side facing viewer, leads down): Emitter (left), Base (center), Collector (right).

Key Features

Applications

Equivalent & Alternatives

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

Compared with ZTX619 (complementary PNP) and MJD127 (higher-voltage TO-220 NPN), the ZTX618 uniquely balances ultra-low V_CE(sat), high h_FE at high current, and TO-92 footprint - making it optimal for space-constrained, low-voltage, high-efficiency gate drive where thermal mass is limited.

Availability

ZTX618 is available at Aetrix Electronics and suitable for power MOSFET gate drivers, DC-DC converter switching stages, linear regulator pass elements, and industrial motor control interfaces requiring stable component supply and long-term manufacturability.

Supply support for ZTX618 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 precision, reliability, and thermal robustness in analog and power semiconductors.

The ZTX series was developed specifically for high-gain, low-saturation switching in compact power management and interface circuits - targeting applications where TO-92 footprint and thermal performance on standard PCBs are critical constraints.

FAQ

What is the maximum safe continuous collector current for ZTX618?

The ZTX618 supports 3.5 A continuous collector current (I_C) at T_amb = 25 °C when mounted on a PCB with ≥1 square inch of copper. Derating applies above 25 °C: power dissipation drops linearly to zero at +200 °C junction temperature, per the published derating curve.

Can ZTX618 be used in parallel configurations?

No - the ZTX618 lacks built-in emitter ballasting resistors and exhibits positive thermal feedback. Parallel operation risks current hogging and thermal runaway. For higher current, use a single higher-rated device like MJD127 or implement active current-sharing circuitry.

Is ZTX618 RoHS compliant and halogen-free?

Yes - Diodes Incorporated certifies the ZTX618 as RoHS 2011/65/EU compliant and halogen-free per IEC 61249-2-21. The device uses lead-free matte tin plating and meets JEDEC J-STD-020 moisture sensitivity level (MSL) 1 for unlimited floor life at ≤30 °C/60% RH.

What is the recommended base resistor value for switching a 3.5 A load?

For saturation at I_C = 3.5 A, use I_B ≥ 50 mA (per datasheet test condition). With V_BE(sat) ≈ 0.93 V and typical 3.3 V or 5 V logic drive, a 68 Ω (for 5 V) or 33 Ω (for 3.3 V) base resistor ensures sufficient overdrive while limiting base current to safe levels.