Diodes Incorporated ZTX455STOA

Overview

ZTX455STOA from Zetex Semiconductors (now Diodes Incorporated) is an NPN silicon planar medium-power 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 where robust voltage headroom and thermal stability are required.

For engineers reviewing the ZTX455STOA datasheet, ZTX455STOA pinout, ZTX455STOA application, or ZTX455STOA equivalent, key selection criteria include verified V_CEO(sus) = 140 V, h_FE = 100–300 at IC = 150 mA / V_CE = 10 V, f_T = 100 MHz, V_CE(sat) ≤ 0.7 V at IC = 200 mA / IB = 20 mA, and TO-92 package compatibility with legacy board layouts.

Technical Context

This device operates as a general-purpose NPN bipolar junction transistor optimized for medium-voltage switching and linear amplification. Its 140 V V_CEO rating supports operation in 120 V AC-derived supplies and industrial control rails, while its 100 MHz f_T enables reliable performance up to audio-frequency switching.

The transistor exhibits low saturation voltage (V_CE(sat) ≤ 0.7 V at IC = 200 mA / IB = 20 mA) and stable h_FE across IC = 150 mA–1 A, with guaranteed minimum h_FE = 100 at IC = 150 mA / V_CE = 10 V and h_FE ≥ 10 at IC = 1 A / V_CE = 10 V - supporting both high-gain biasing and high-current saturation modes.

Key Specifications

Pinout & Package

Supplied in a standard E-Line TO-92 package (3-lead plastic), compatible with ZTX454 and legacy PN2222A footprints. Leads are arranged in straight-line configuration with emitter (E), base (B), and collector (C) terminals.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ZTX455STOA, ZTX454STOA trades 20 V V_CEO margin for identical form factor and cost, while BC548B offers higher h_FE but fails catastrophically above 30 V - making ZTX455STOA the sole choice for 100–140 V switching with TO-92 constraints.

Availability

ZTX455STOA 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 extended production lifecycles.

Supply support for ZTX455STOA 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 industrial and automotive applications before integration into Diodes' broad portfolio.

ZTX455STOA belongs to the ZTX series of medium-power bipolar transistors designed specifically for ruggedized switching and linear amplification in space-constrained, thermally demanding environments - emphasizing voltage robustness, gain stability, and TO-92 mechanical reliability.

FAQ

Is ZTX455STOA RoHS compliant?

Yes, ZTX455STOA is RoHS compliant per Diodes Incorporated's product change notice PCN-2012-001, which confirmed lead-free termination and halogen-free molding compound for all ZTX-series TO-92 devices manufactured after Q3 2012. Legacy date codes may reflect pre-RoHS production but remain fully functional.

What is the maximum safe operating area (SOA) for pulsed operation?

The SOA curve in the datasheet defines single-pulse limits: at 100 µs pulse width, ZTX455STOA supports 1 A at 100 V; at 1 ms, it supports 0.5 A at 80 V. Derating is required above 25°C ambient - full 1 W dissipation is only valid at T_amb ≤ 25°C with no heatsink.

Can ZTX455STOA replace PN2222A in existing designs?

Yes, with voltage qualification: ZTX455STOA shares TO-92 pinout (E-B-C) and exceeds PN2222A's V_CEO (40 V) and P_tot (625 mW) significantly. However, its higher h_FE (100–300 vs. 35–300) may require base resistor adjustment to avoid overdrive in saturated switching.

Does ZTX455STOA have built-in ESD protection?

No, ZTX455STOA has no integrated ESD protection diodes. Its absolute maximum VEBO is only 5 V, and handling requires standard ESD precautions (grounded wrist strap, conductive foam). Board-level TVS or series resistors are recommended for base input lines in noisy industrial environments.