Diodes Incorporated ZTX955

Overview

ZTX955 from Zetex Semiconductors (now Diodes Incorporated) is a PNP silicon planar medium-power high-current transistor designed for linear and switching applications in industrial power control, relay drivers, and DC-DC converter output stages. It delivers -3 A continuous collector current, -140 V V_CEO, -90 mV V_CE(sat) at -3 A/-300 mA drive, and 100–300 h_FE across 10 mA–3 A, operating reliably from -55°C to +200°C.

For engineers reviewing the ZTX955 datasheet, ZTX955 pinout, ZTX955 application, or ZTX955 equivalent, key selection criteria include its low saturation voltage under high current, robust safe operating area up to 10 A peak, thermal resistance of 50°C/W (junction-to-case), and TO-92-compatible E-Line package suitability for PCB-mounted medium-power amplification and switching.

Technical Context

The ZTX955 operates as a medium-power PNP bipolar junction transistor with a planar silicon structure optimized for high-current linear and saturated switching. Its gain remains stable (h_FE ≥100) up to -3 A at V_CE = -5 V, and it supports fast switching with t_on = 68 ns and t_off = 1030 ns under defined pulsed conditions (I_C = -1 A, V_CC = -50 V).

Thermal design is enabled by a 50°C/W junction-to-case thermal resistance and a 150°C/W junction-to-ambient rating on a 1-inch² copper pad. The device features a V_(BR)CEO of -140 V (min), V_(BR)CBO of -180 V (min), and V_BE(sat) of -920 mV at -3 A/-300 mA - confirming strong base drive efficiency in high-current saturation.

Key Specifications

Pinout & Package

Package: E-Line TO-92-compatible (3-321 outline), epoxy-molded, through-hole mount with emitter (E), base (B), and collector (C) leads arranged in linear C-B-E order when viewed with flat side facing up and leads downward.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar PNP high-current switching applications.

Compared with MJD2955 and BCX69-16, the ZTX955 uniquely balances TO-92 mountability, -140 V voltage rating, and -90 mV saturation voltage - making it optimal for space-constrained, medium-voltage industrial switching where thermal management relies on PCB copper rather than external heatsinks.

Availability

ZTX955 is available at Aetrix Electronics and suitable for industrial relay drivers, linear regulator pass elements, DC-DC converter output stages, and high-temperature sensor interfaces requiring stable component supply across extended temperature ranges and multi-year production cycles.

Supply support for ZTX955 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, now part of Diodes Incorporated, specialized in high-performance discrete semiconductors for precision analog and power management applications before its 2008 acquisition.

The ZTX series was developed specifically for ruggedized medium-power linear and switching applications demanding wide temperature operation, low saturation voltage, and reliable gain stability - targeting industrial automation, power conversion, and harsh-environment electronics.

FAQ

Is ZTX955 RoHS compliant?

Yes, ZTX955 is RoHS compliant per Diodes Incorporated's product change notices and material declarations. The device uses lead-free terminations and halogen-free molding compound, meeting EU Directive 2011/65/EU requirements without exemptions. Compliance applies to all current production lots shipped after 2010.

Can ZTX955 be used in avalanche mode?

No, ZTX955 is not rated or characterized for intentional avalanche operation. Its absolute maximum V_(BR)CER (-180 V) reflects short-pulse breakdown with R_B ≤1 kΩ, but no energy-rated SOA curve or repetitive avalanche specifications are provided in the datasheet. Use within the defined Safe Operating Area only.

What is the recommended PCB layout for thermal performance?

For optimal thermal performance, mount ZTX955 on a minimum 1-inch² copper pour connected directly to the collector (tab) via multiple thermal vias. Avoid solder mask over the copper area. Keep traces to base and emitter short and wide; use ≥15 mil trace width for collector current paths to limit resistive heating and voltage drop.

Does ZTX955 have a built-in base-emitter resistor?

No, ZTX955 is a standard three-terminal PNP bipolar transistor with no integrated base-emitter resistor. External base drive circuitry - including current-limiting resistors and optional Baker clamp networks - must be implemented per application requirements to ensure proper saturation and prevent secondary breakdown.