Diodes Incorporated ZTX457

Overview

ZTX457 from Diodes Incorporated is an NPN silicon planar medium-power high-voltage transistor with 300 V V_CEO, 500 mA continuous collector current, and 1 W power dissipation at 25°C ambient-designed for switching and linear amplification in high-voltage industrial power supplies and relay drivers.

For engineers reviewing the ZTX457 datasheet, ZTX457 pinout, ZTX457 application, or ZTX457 equivalent, key selection criteria include verified 300 V breakdown rating, h_FE range of 50–300 at 10–100 mA I_C, pulsed f_T of 75 MHz, and TO-92 package thermal limits under sustained conduction.

Technical Context

This transistor employs a planar epitaxial structure optimized for stable high-voltage operation up to 300 V V_CEO and 200°C junction temperature. Its h_FE is specified across three collector current points (10/50/100 mA), supporting predictable gain behavior in both switching and analog biasing configurations.

Electrical testing follows pulsed conditions (300 µs width, ≤2% duty cycle) for V_CE(sat), V_BE(sat), and f_T measurements, ensuring validity under transient load conditions typical in relay coil driving and flyback snubber circuits.

Key Specifications

Pinout & Package

Supplied in E-Line TO-92 compatible package (3-181 outline), with standard C-B-E lead assignment confirmed by manufacturer marking and mechanical drawing.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ZTX457, ZTX450 trades 50 V breakdown headroom for broader availability, while BCV46 sacrifices power capability for smaller TO-92 footprint-neither matches ZTX457's combined 300 V/500 mA/1 W specification set.

Availability

ZTX457 is available at Aetrix Electronics and suitable for industrial relay drivers, DC-DC converter switches, and high-voltage linear regulators requiring stable component supply across extended temperature and voltage ranges.

Supply support for ZTX457 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 semiconductor company specializing in discrete, analog, and mixed-signal devices for industrial, computing, and consumer markets.

ZTX457 belongs to the ZTX series of high-voltage bipolar transistors engineered for reliable switching and amplification in mains-connected power systems and ruggedized control hardware.

FAQ

Is ZTX457 suitable for switching 240 VAC-derived DC bus voltages?

Yes. With 300 V V_CEO and 300 V V_CBO, ZTX457 safely switches rectified 240 VAC (≈340 V peak) when operated with appropriate snubbing and derating. Its 200°C maximum junction temperature further supports reliability under sustained conduction at elevated ambient temperatures.

What is the minimum base current required to saturate ZTX457 at 500 mA collector current?

Per datasheet, V_CE(sat) = 0.3 V is guaranteed at I_C = 100 mA and I_B = 10 mA (h_FE ≥ 10). At 500 mA, assuming h_FE ≥ 50, minimum I_B = 10 mA is recommended. For robust saturation across temperature and lot variation, 15–20 mA base drive is advised.

Can ZTX457 replace ZTX458 in existing designs?

No. ZTX458 is a PNP complement with identical voltage/current ratings but opposite polarity. Swapping requires circuit-level inversion of bias networks, load connections, and protection diodes. The two devices are not functionally interchangeable without schematic revision.

Does ZTX457 require a heatsink in 1 W continuous operation?

Yes. At 1 W dissipation and 25°C ambient, the TO-92 package thermal resistance (R_θJA) exceeds 200°C/W. Without copper pour or heatsinking, junction temperature would exceed 200°C. A minimum 1 cm² 2-oz copper pad is required to maintain T_j ≤ 150°C at full power.