Diodes Incorporated ZTX457STOA

Overview

ZTX457STOA 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. It serves as a switching or linear amplifier in high-voltage industrial power supplies, relay drivers, and lamp ballasts where robust breakdown voltage and thermal stability up to +200°C are required.

For engineers reviewing the ZTX457STOA datasheet, ZTX457STOA pinout, ZTX457STOA application, or ZTX457STOA equivalent, key selection criteria include verified 300 V V_CEO, pulsed I_CM = 1 A capability, TO-92-compatible E-Line package footprint, h_FE range of 25–300 at I_C = 10–100 mA, and validated operation across –55°C to +200°C junction temperature.

Technical Context

This transistor uses a planar epitaxial structure optimized for high-voltage blocking and medium-current switching. Its V_(BR)CBO and V_CEO(sus) are both rated at 300 V under specified test conditions (I_C = 100 µA and I_C = 10 mA respectively), confirming stable avalanche immunity in off-state.

The device exhibits V_CE(sat) = 0.3 V at I_C = 100 mA / I_B = 10 mA and V_BE(sat) = 1 V under identical conditions, supporting efficient low-loss saturation in driver stages. Transition frequency f_T = 75 MHz at I_C = 50 mA / V_CE = 10 V enables use in audio-frequency amplification and fast-switching control loops.

Key Specifications

Pinout & Package

Package: TO-92-compatible E-Line (3-181), through-hole, epoxy-molded, lead-form compatible with standard TO-92 sockets and wave-solder processes.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ZTX457STOA, ZTX450 trades voltage headroom for tighter h_FE distribution, while BCV46 sacrifices current capacity and mounting compatibility for miniaturization-neither offers full functional equivalence in high-current, through-hole, 300 V applications.

Availability

ZTX457STOA is available at Aetrix Electronics and suitable for industrial power supplies, lamp ballasts, relay driver circuits, and overvoltage protection switches requiring stable component supply across extended temperature and high-voltage operating conditions.

Supply support for ZTX457STOA 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 components for industrial, automotive, and computing markets.

ZTX457STOA belongs to the ZTX series of high-voltage bipolar transistors designed specifically for ruggedized switching and amplification in mains-connected equipment and harsh-environment controls.

FAQ

Is ZTX457STOA RoHS compliant?

Yes, ZTX457STOA meets RoHS Directive 2011/65/EU requirements. Diodes Incorporated confirms lead-free terminations, halogen-free molding compound, and full compliance documentation available upon request for production traceability and regulatory submission.

What is the maximum safe operating area (SOA) for ZTX457STOA at 100°C case temperature?

At T_C = 100°C, the SOA is defined by the 300 V V_CEO limit, 500 mA I_C limit, and thermal resistance R_θJC = 125°C/W. Derated power dissipation is approximately 0.4 W; operation beyond this requires active cooling or pulse-width limitation per the manufacturer's SOA graph in Issue 2 datasheet.

Can ZTX457STOA replace ZTX458 in existing designs?

No-ZTX458 is a PNP counterpart with identical voltage/current ratings but opposite polarity. Direct substitution would invert logic and cause circuit failure. A true NPN-to-NPN replacement requires matching h_FE curve, V_CE(sat), and thermal profile-not just package or voltage specs.

Does ZTX457STOA require a base resistor in switching applications?

Yes-a series base resistor is mandatory to limit I_B and ensure saturation without exceeding I_B(max). For I_C = 500 mA and minimum h_FE = 25, I_B ≥ 20 mA is required; typical design uses 470 Ω–1 kΩ depending on drive voltage and safety margin.