Diodes Incorporated ZTX605

Overview

ZTX605 from Zetex Semiconductors (now Diodes Incorporated) is an NPN silicon planar medium-power Darlington transistor in a TO-92 package, rated for 120 V_CEO, 1 A continuous collector current, and 1 W power dissipation at 25°C ambient. It delivers h_FE ≥2000 at I_C = 1 A, V_CE = 5 V, with V_CE(sat) ≤1.5 V and V_BE(sat) = 1.8 V - used in high-gain switching and linear amplification stages of industrial control relays and DC motor drivers.

For engineers reviewing the ZTX605 datasheet, ZTX605 pinout, ZTX605 application, or ZTX605 equivalent, key selection criteria include verified Darlington gain stability at 1 A, safe operating area under pulsed 4 A peak conditions, thermal derating compliance up to +200°C junction temperature, and TO-92 mechanical compatibility with legacy board layouts.

Technical Context

The ZTX605 implements a monolithic Darlington pair architecture with integrated base-emitter resistor network enabling direct TTL/CMOS drive without external biasing. Its 120 V_CEO rating supports operation across 24–48 V industrial bus systems, while f_T = 150 MHz ensures adequate bandwidth for fast-switching applications up to ~100 kHz duty-cycled loads.

Electrical behavior is characterized by low V_CE(sat) (1.0–1.5 V) at I_C/I_B = 100, tight V_BE(on) = 1.7 V tolerance, and C_ibo = 90 pF / C_obo = 15 pF capacitance values that minimize Miller effect during turn-off transitions in inductive load switching.

Key Specifications

Pinout & Package

Package: TO-92 (E-Line compatible), through-hole, epoxy-molded plastic case with standard lead spacing (0.1" pitch). Pin identification follows emitter-base-collector (E-B-C) sequence when viewing flat side with leads downward.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MPSA14 and BC517, the ZTX605 uniquely combines 120 V blocking, 1 A continuous current, and ≥2000 h_FE in TO-92 - making it irreplaceable in industrial 48 V relay drivers and thermally constrained motor control stages requiring single-device simplicity.

Availability

ZTX605 is available at Aetrix Electronics and suitable for industrial relay drivers, DC motor speed control, thermal cut-off circuits, and linear voltage regulator pass elements requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for ZTX605 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

Zetex Semiconductors was a UK-based analog and discrete semiconductor specialist acquired by Diodes Incorporated in 2008; known for high-reliability bipolar transistors and precision analog ICs.

The ZTX series targets medium-power discrete switching and amplification, designed specifically for industrial control, power management, and ruggedized embedded systems demanding wide temperature operation and mechanical robustness.

FAQ

What is the maximum pulsed collector current rating for ZTX605?

The ZTX605 supports I_CM = 4 A peak pulse current under pulsed conditions (pulse width = 300 µs, duty cycle ≤2%). This value is validated by its Safe Operating Area curve on page 3-213 of the official datasheet and applies only when junction temperature remains within +200°C limit and thermal mass prevents cumulative heating.

Can ZTX605 be used in linear amplifier configurations?

Yes - the ZTX605 is characterized for linear operation with specified h_FE, V_BE(on), and V_CE(sat) across I_C = 0.01–2 A. Its 150 MHz f_T and low output capacitance (C_obo = 15 pF) support audio-frequency amplification, though thermal derating must be applied above 25°C ambient to maintain P_tot ≤1 W.

Is ZTX605 RoHS compliant and halogen-free?

Yes - as part of Diodes Incorporated's post-acquisition product line, ZTX605 meets RoHS Directive 2011/65/EU and is certified halogen-free per IEC 61249-2-21. The TO-92 package uses lead-free matte tin plating and green epoxy molding compound, with full compliance documentation available under Diodes' QG-001 specification.

How does ZTX605 compare to ZTX604 in practical use?

ZTX605 offers higher V_CEO (120 V vs. 100 V) and V_CBO (140 V vs. 120 V) than ZTX604, with identical pinout and package. Both share 1 A I_C, 1 W P_tot, and ≥2000 h_FE at 1 A. ZTX605 is preferred for 48 V systems or designs requiring extra transient margin; ZTX604 remains valid where 100 V rating suffices and legacy BOMs mandate exact cross-reference.