Diodes Incorporated FZT851TA

Overview

FZT851TA from Diodes Incorporated is a 60V, 6A NPN medium-power transistor in SOT223 package, featuring V_CE(sat) < 100 mV at 1 A and R_CE(sat) = 44 mΩ, with h_FE specified up to 10 A. It serves as a high-current switching element in DC-DC converters, motor drivers, and LED power stages.

For engineers reviewing the FZT851TA datasheet, FZT851TA pinout, FZT851TA application, or FZT851TA equivalent, key selection criteria include verified 6 A continuous current capability, low 44 mΩ on-resistance, AEC-Q101 qualification for automotive use, thermal resistance of 42 °C/W (52 mm × 52 mm 2 oz Cu), and complementary PNP pairing with FZT951.

Technical Context

This NPN bipolar junction transistor operates in linear and saturated switching modes, with BV_CEO = 60 V and peak pulse current I_CM = 20 A. Its gain-bandwidth product f_t = 130 MHz supports fast-switching applications up to several hundred kHz.

The device uses a planar epitaxial die structure with low saturation voltage design, enabling efficient operation under high-current DC loads. Thermal performance is defined for two PCB mounting conditions: R_θJA = 42 °C/W (52 mm × 52 mm 2 oz Cu) and 78 °C/W (25 mm × 25 mm 1 oz Cu).

Key Specifications

Pinout & Package

SOT223 (Type DN) surface-mount package with three terminals: Collector (tab), Emitter (pin 1), Base (pin 2). The exposed collector tab provides low thermal resistance path to PCB copper.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar NPN medium-power transistor applications.

Compared with ZXTN2012E6TA and MJD127G, FZT851TA uniquely balances 6 A current, SOT223 compactness, AEC-Q101 compliance, and 44 mΩ on-resistance-making it optimal for space-constrained automotive and industrial power switches where reliability and thermal efficiency are jointly critical.

Availability

FZT851TA is available at Aetrix Electronics and suitable for automotive LED drivers, industrial DC-DC converters, brushed motor controllers, and redundant power OR-ing circuits requiring stable component supply and long-term lifecycle support.

Supply support for FZT851TA 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 North America.

FZT851TA belongs to Diodes' medium-power bipolar transistor product line, engineered for high-current switching in automotive and industrial power conversion where reliability, thermal performance, and AEC-Q101 compliance are mandatory.

FAQ

Is FZT851TA pin-compatible with FZT851QTA?

Yes - both share identical SOT223 pinout (Collector tab, Emitter pin 1, Base pin 2) and mechanical footprint. FZT851QTA adds AEC-Q101 qualification and automotive-specific change control, while FZT851TA is the commercial-grade variant with identical electrical specs and thermal ratings.

What is the maximum allowable PCB copper area for thermal optimization?

The datasheet specifies R_θJA = 42 °C/W when mounted on a 52 mm × 52 mm 2 oz copper area. Increasing copper beyond this yields diminishing returns; minimum recommended is 25 mm × 25 mm 1 oz Cu (R_θJA = 78 °C/W). Thermal vias under the collector tab further improve performance.

Can FZT851TA replace a MOSFET in low-side switching applications?

It can function as a BJT alternative where gate drive simplicity and cost matter, but lacks MOSFET advantages like zero gate current and lower drive complexity. Use only when V_CE(sat) loss is acceptable and base drive current (≥300 mA at 6 A) is feasible within system constraints.

Does FZT851TA require a base resistor, and what value is recommended?

Yes - a series base resistor is mandatory to limit IB and prevent thermal runaway. For 6 A collector current with h_FE ≥ 25, IB ≥ 240 mA is needed; with 5 V drive, a 15 Ω ±5% resistor delivers ~233 mA, ensuring saturation while allowing margin for h_FE variation across temperature.