Diodes Incorporated FZT458TA

Overview

FZT458TA from Diodes Incorporated is a 400V NPN medium-power transistor in SOT223 package, designed for high-voltage switching in industrial power supplies and LED drivers. It delivers 300mA continuous collector current, exhibits V_CE(sat) < 200mV at 20mA/2mA drive, and maintains h_FE ≥ 100 up to 100mA - enabling efficient linear and switching operation in flyback snubber and relay driver circuits.

For engineers reviewing the FZT458TA datasheet, FZT458TA pinout, FZT458TA application, or FZT458TA equivalent, key selection criteria include its 400V V_CEO rating, low saturation voltage under moderate drive, thermal resistance of 41.7°C/W on 50mm × 50mm copper, and complementary pairing with FZT558 for push-pull topologies.

Technical Context

This NPN bipolar junction transistor operates in active, saturation, and cutoff regions with guaranteed BV_CEO = 400V and V_EBO = 7V, supporting high-side switching in off-line AC-DC converters where primary-side voltage transients exceed 300V. Its f_T = 50MHz ensures adequate bandwidth for PWM frequencies up to several hundred kHz.

The device uses a planar epitaxial structure with optimized base doping and emitter geometry to achieve stable h_FE across -55°C to +150°C, while its 19.41°C/W R_θJL enables direct thermal coupling to PCB copper pour - critical for sustained 2W dissipation without heatsink in space-constrained designs.

Key Specifications

Pinout & Package

Package: SOT223 (Type DN), surface-mount, 4-pin configuration with collector tab electrically connected to Pin 1 (Collector). Molded green compound, UL 94V-0 rated, 0.112g weight.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ZTX458 and MJD44H11T4G, FZT458TA uniquely balances 400V capability, SOT223 compactness, and sub-200mV saturation in a single component - making it optimal for cost-sensitive, high-density 1–5W power interfaces where thermal mass is limited.

Availability

FZT458TA is available at Aetrix Electronics and suitable for industrial power supply snubbers, LED constant-current drivers, and automotive relay drivers requiring stable component supply with full traceability and long-term lifecycle support.

Supply support for FZT458TA 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, headquartered in Plano, Texas, with design, manufacturing, and sales operations across Asia, Europe, and the Americas.

FZT458TA belongs to Diodes' high-voltage bipolar transistor product line, engineered specifically for reliable switching and linear regulation in off-line power conversion, lighting, and automotive subsystems where voltage robustness and thermal efficiency are critical.

FAQ

Is FZT458TA qualified for automotive applications per AEC-Q101?

No - FZT458TA is not AEC-Q101 qualified. While it meets industrial temperature range (-55°C to +150°C) and has green/halogen-free construction, Diodes specifies that automotive-grade versions require explicit PPAP documentation and IATF 16949 manufacturing - which this part number does not carry. Customers needing automotive qualification must contact Diodes directly for AEC-Q101-compliant variants.

What is the maximum allowable PCB copper area for thermal performance without heatsink?

For 2W continuous operation at 25°C ambient, Diodes specifies a minimum 50mm × 50mm (2oz copper) pad connected to Pin 1 (collector tab) to achieve R_θJA = 41.7°C/W. Smaller pads increase thermal resistance: a 25mm × 25mm pad raises R_θJA to 62.5°C/W, limiting safe continuous power to ~1.2W at 25°C ambient.

Can FZT458TA replace BCV61B in a 24V relay driver?

No - BCV61B is a dual NPN in SOT-363 with V_CEO = 60V and I_C = 100mA. FZT458TA's 400V rating and 300mA I_C far exceed BCV61B's specs, but its SOT223 footprint, single-transistor configuration, and higher drive requirement make it incompatible as a direct replacement without PCB redesign and base resistor recalculation.

Does FZT458TA have integrated ESD protection beyond HBM 4000V?

No - the datasheet specifies only JEDEC-standard Human Body Model (HBM) 4000V and Machine Model (MM) 400V ESD ratings. There is no mention of CDM (Charged Device Model) rating, IEC 61000-4-2 compliance, or internal transient suppression circuitry. External TVS or RC filtering is recommended for board-level ESD immunity in end equipment.