Diodes Incorporated ZTX957STOA

Overview

ZTX957STOA from Diodes Incorporated is a PNP silicon planar medium-power high-current bipolar junction transistor (BJT), designed for switching and linear amplification in industrial power control circuits. It delivers −1 A continuous collector current, −300 V V_CEO, and −140 mV V_CE(sat) at I_C = −1 A / I_B = −300 mA, with h_FE ≥ 100 at I_C = −1 A, enabling robust high-voltage DC-DC converter output stage operation.

For engineers reviewing the ZTX957STOA datasheet, ZTX957STOA pinout, ZTX957STOA application, or ZTX957STOA equivalent, key selection criteria include verified −300 V blocking capability, low −140 mV saturation voltage under full-rated current, thermal resistance of 150 °C/W (junction-to-ambient), TO-92 package compatibility, and SPICE model availability for circuit simulation validation.

Technical Context

The ZTX957STOA operates as a high-voltage PNP switch with avalanche-rated breakdown (V_CEO = −300 V, V_CBO = −330 V) and supports pulsed peak currents up to −2 A. Its gain remains stable across I_C = −10 mA to −1 A (h_FE = 100–200), and it exhibits f_T = 85 MHz at I_C = −100 mA, supporting fast-switching applications up to mid-MHz frequencies.

Thermal design relies on its R_th(j-amb) = 150 °C/W (on 1-inch² PCB copper) and R_th(j-case) = 50 °C/W, with safe operating area (SOA) validated for single-pulse and DC conditions up to +175 °C junction temperature. Saturation voltage is characterized across −55 °C to +175 °C, confirming performance stability in wide-temperature industrial environments.

Key Specifications

Pinout & Package

Package: TO-92 (E-Line compatible, 3-327 outline), through-hole mounting, epoxy encapsulated, lead-free compliant.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ZTX951 and MJD2955G, the ZTX957STOA uniquely balances −300 V blocking, −140 mV saturation, and TO-92 form factor-making it optimal for space-constrained, high-voltage industrial controls where thermal and voltage margins cannot be compromised.

Availability

ZTX957STOA is available at Aetrix Electronics and suitable for industrial relay drivers, high-voltage DC-DC converters, motor brake circuits, and linear regulator pass elements requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for ZTX957STOA 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 is a global leader in discrete semiconductors and analog ICs, specializing in high-reliability components for industrial, automotive, and computing markets with ISO/TS 16949 and ISO 14001 certification.

The ZTX957STOA belongs to Diodes' ZTX series of high-voltage bipolar transistors, engineered specifically for ruggedized industrial power switching where voltage margin, thermal stability, and SPICE-model fidelity are critical.

FAQ

What is the maximum safe operating junction temperature for ZTX957STOA?

The ZTX957STOA has a specified operating junction temperature range of −55 °C to +200 °C, with SOA curves validated up to +175 °C for continuous operation. Derating begins at +25 °C ambient per the 150 °C/W thermal resistance curve, and sustained operation above +175 °C risks permanent parametric shift or bond-wire failure.

Does ZTX957STOA require a heatsink in TO-92 mounting?

No heatsink is required for ZTX957STOA at ≤1 A continuous current when mounted on a 1-inch² copper pad per the datasheet's "practical power dissipation" condition (P_totp = 1.58 W). At full 1.2 W dissipation (P_tot), junction temperature rises ~180 °C above ambient-so natural convection suffices only if ambient stays below +20 °C; otherwise, modest copper pour extension is recommended.

Can ZTX957STOA replace ZTX953 in existing designs?

Yes-ZTX957STOA shares the same E-Line TO-92 package (3-327) and pinout (E-B-C), with identical footprint and soldering profile. It improves upon ZTX953 with higher V_CEO (−300 V vs. −250 V), lower V_CE(sat) (−140 mV vs. −180 mV), and wider SOA, making it a direct performance upgrade without layout changes.

Is SPICE model availability confirmed for ZTX957STOA?

Yes-the manufacturer explicitly lists "Spice model available" in the official datasheet (Issue 3, June 1994) and provides a downloadable .lib file on Diodes Incorporated's product page for ZTX957. The model includes temperature-dependent parameters, junction capacitance, and switching dynamics validated against production characterization data.