Diodes Incorporated ZTX457STOB

Overview

ZTX457STOB from Diodes Incorporated is an NPN silicon planar medium-power high-voltage transistor with V_CEO = 300 V, I_C = 500 mA, P_tot = 1 W, and f_T = 75 MHz at 50 mA/10 V; used in flyback switchers, CRT deflection, and industrial HV switching circuits.

For engineers reviewing the ZTX457STOB datasheet, ZTX457STOB pinout, ZTX457STOB application, or ZTX457STOB equivalent, key selection criteria include verified 300 V blocking capability, h_FE range of 50–300 across 10–100 mA I_C, TO-92-compatible E-Line package thermal performance, and pulsed-switching suitability per 300 µs/2% duty cycle test conditions.

Technical Context

This transistor employs a planar epitaxial structure optimized for stable high-voltage operation up to 300 V in both V_CBO and V_CEO configurations, with guaranteed minimum h_FE of 50 at 10 mA and maximum V_CE(sat) of 0.3 V at 100 mA/10 mA drive.

Its f_T of 75 MHz at 50 mA/10 V supports moderate-speed switching in SMPS and line-output stages; breakdown ratings are validated under pulsed conditions (300 µs width, ≤2% duty cycle), ensuring robustness in repetitive transient environments.

Key Specifications

Pinout & Package

E-Line TO-92-compatible package: molded plastic case with 3.3 mm lead spacing, 4.5 mm body height, and standard through-hole mounting footprint; thermally rated for 1 W dissipation with adequate copper pour.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ZTX457STOB, ZTX450 trades 50 V headroom and 10 points of minimum h_FE for lower cost, while BCW66G offers higher current but fails catastrophically above 60 V-making ZTX457STOB uniquely suited for 200–300 V industrial switching where reliability and voltage margin are non-negotiable.

Availability

ZTX457STOB is available at Aetrix Electronics and suitable for flyback switchers, CRT deflection circuits, and industrial relay drivers requiring stable component supply across extended temperature ranges (−55°C to +200°C).

Supply support for ZTX457STOB 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 manufacturer of discrete semiconductors and analog ICs, specializing in high-reliability power management and signal integrity solutions for industrial and automotive markets.

ZTX457STOB belongs to the ZTX series of high-voltage bipolar transistors designed specifically for ruggedized switching in off-line power conversion, display deflection, and industrial control systems.

FAQ

What is the maximum safe operating voltage for ZTX457STOB in continuous DC mode?

ZTX457STOB is rated for continuous collector-emitter voltage (V_CEO) of 300 V at T_j ≤ 150°C. Operation above this value risks avalanche breakdown even with heatsinking. Derating is required above 25°C ambient per the thermal resistance curve in the official datasheet Issue 2 (March 1994), with absolute max junction temperature limited to +200°C.

Can ZTX457STOB be used in surface-mount designs?

No-ZTX457STOB uses an E-Line TO-92-compatible through-hole package with 3.3 mm lead pitch and axial leads. It lacks SMT-compatible terminations or footprint. For surface-mount equivalents, consider Diodes Inc.'s DXT75100 (SOT-23, 100 V) or Zetex's FMMT457 (SOT-23, 300 V), though neither matches the exact thermal or gain profile.

What base drive current is required to fully saturate ZTX457STOB at 500 mA collector load?

At I_C = 500 mA, saturation requires I_B ≥ 50 mA based on h_FE(min) = 50 at 10 mA and typical gain roll-off at high current. The datasheet specifies V_CE(sat) = 0.3 V at I_C = 100 mA / I_B = 10 mA; extrapolation confirms ≥10:1 overdrive ratio needed for full saturation at rated I_C.

Is ZTX457STOB compliant with RoHS or halogen-free standards?

ZTX457STOB was released in March 1994, predating RoHS (2006) and halogen-free mandates. Diodes Incorporated does not list it in current RoHS-compliant product portfolios. For new designs requiring compliance, consult Diodes' ZTX653 (RoHS-compliant, 300 V, TO-92) or contact Aetrix for qualified drop-in alternatives with full environmental certification.