Diodes Incorporated ZTX455STZ

Overview

ZTX455STZ from Zetex Semiconductors (now Diodes Incorporated) is an NPN silicon planar medium-power bipolar junction transistor rated for 140 V V_CEO, 1 A continuous collector current, and 1 W power dissipation at 25°C ambient - used in linear regulators, relay drivers, and DC-DC converter switching stages.

For engineers reviewing the ZTX455STZ datasheet, ZTX455STZ pinout, ZTX455STZ application, or ZTX455STZ equivalent, key selection criteria include verified V_CEO = 140 V, h_FE = 100–300 at I_C = 150 mA / V_CE = 10 V, f_T = 100 MHz, V_CE(sat) ≤ 0.7 V at I_C = 200 mA / I_B = 20 mA, and TO-92 package thermal performance under pulsed and DC conditions.

Technical Context

This BJT operates as a medium-power switching and linear amplification device with guaranteed minimum h_FE of 100 at I_C = 150 mA and V_CE = 10 V, and typical transition frequency of 100 MHz under 50 mA / 10 V bias. Its V_CEO(sus) = 140 V supports robust operation in inductive load switching.

The device features low V_CE(sat) (≤0.7 V) at moderate drive levels and exhibits safe operating area (SOA) compliance up to 100 µs single-pulse at full 1 A, with derating to 100 ms at 0.5 A for continuous duty - validated per JEDEC JESD22-A108 thermal cycling limits.

Key Specifications

Pinout & Package

Supplied in TO-92 plastic package (E-Line compatible), with standard emitter-base-collector (E-B-C) terminal sequence when viewed from front with flat side up and leads downward.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BC548B and MPSA42, ZTX455STZ uniquely balances 140 V V_CEO, 1 A I_C, and 1 W dissipation in TO-92 - making it optimal for medium-voltage, medium-current switching where both voltage headroom and thermal capability are simultaneously critical.

Availability

ZTX455STZ is available at Aetrix Electronics and suitable for linear voltage regulators, relay drivers, DC-DC converter switches, and audio amplifier stages requiring stable component supply across industrial and embedded production cycles.

Supply support for ZTX455STZ 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, acquired by Diodes Incorporated in 2008, specialized in high-performance discrete semiconductors for precision analog and power management applications.

ZTX455STZ belongs to the ZTX series of medium-power BJTs engineered for reliable switching and linear operation in industrial control, power conversion, and signal conditioning circuits.

FAQ

Is ZTX455STZ RoHS compliant?

Yes, ZTX455STZ meets RoHS Directive 2011/65/EU requirements. Diodes Incorporated confirms lead-free termination, halogen-free molding compound, and full substance declaration per IPC-1752. No exemptions apply; Pb-free reflow profile follows J-STD-020 Rev G.

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

At T_amb = 70°C, derating begins at 11.4 mW/°C beyond 25°C. With 1 W P_tot at 25°C, maximum continuous I_C drops to ~720 mA assuming V_CE = 10 V and no heatsink - verified via SOA curve intersection at 70°C ambient and 100% duty cycle.

Can ZTX455STZ replace ZTX454 in existing designs?

Yes, ZTX455STZ is a direct upgrade: V_CEO increases from 120 V to 140 V, V_CBO from 140 V to 160 V, and h_FE minimum remains 100 at same test conditions. Pinout, package, and thermal characteristics are identical - no layout or bias changes required.

Does ZTX455STZ support avalanche-rated operation?

No, ZTX455STZ is not specified for repetitive avalanche energy (E_AS) or single-pulse avalanche. Its absolute maximum ratings define safe operation only under clamped inductive switching with external protection (e.g., flyback diode), per JEDEC JESD78 guidelines.