Diodes Incorporated ZTX849STOA

Overview

ZTX849STOA from Diodes Incorporated is an NPN silicon planar medium-power high-current transistor designed for switching and amplification in DC-DC converter stages, motor drive half-bridges, and battery-powered load interfaces. It delivers 5 A continuous collector current, supports 20 A peak pulses, achieves V_CE(sat) as low as 25 mV at I_C=0.5 A/ I_B=20 mA, and operates with V_CEO = 30 V - enabling use in LCD backlight boost converters and flash gun power stages.

For engineers reviewing the ZTX849STOA datasheet, ZTX849STOA pinout, ZTX849STOA application, or ZTX849STOA equivalent, key selection criteria include verified saturation voltage at high I_C/I_B ratios, thermal resistance (R_th(j-amb) = 150 °C/W), safe operating area under pulsed loads, and TO-92 mechanical compatibility with E-Line footprint.

Technical Context

This NPN bipolar junction transistor uses a planar epitaxial structure optimized for high-current switching with low V_CE(sat) and fast turn-on/turn-off times (t_on = 45 ns, t_off = 630 ns). Its h_FE ranges from 100 at I_C = 10 mA to 65 at I_C = 5 A (V_CE = 1 V), supporting stable gain across medium-load conditions.

The device features robust breakdown ratings: V_(BR)CEO = 30 V (min), V_(BR)CBO = 80 V (min), and V_(BR)EBO = 6 V (min), with thermal limits spanning –55 °C to +200 °C junction temperature. Its R_th(j-case) = 50 °C/W enables effective heat transfer when mounted on PCB copper areas ≥1 inch².

Key Specifications

Pinout & Package

Package: TO-92 (E-Line compatible, 3-lead plastic package with standard lead pitch and outline per 3-291).

Key Features

Applications

Equivalent & Alternatives

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

Compared with ZTX851STOA and BCX56-16, ZTX849STOA uniquely balances 5 A continuous current, 30 V V_CEO, and sub-200 mV V_CE(sat) in TO-92 - making it optimal for cost-sensitive, medium-power battery-fed switching where voltage and current requirements align precisely.

Availability

ZTX849STOA is available at Aetrix Electronics and suitable for LCD backlight converters, flash gun power stages, and battery-powered motor drivers requiring stable component supply and long-term manufacturing continuity.

Supply support for ZTX849STOA 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, high-efficiency components for power management, signal integrity, and protection.

ZTX849STOA belongs to the ZTX series of high-current bipolar transistors engineered for ruggedized switching in portable and industrial power conversion systems where TO-92 form factor and thermal performance are critical.

FAQ

What is the maximum safe continuous collector current for ZTX849STOA at 70°C ambient?

At T_amb = 70°C, derating from the 1.2 W P_tot (25°C) applies. With R_th(j-amb) = 150 °C/W, junction temperature rise is 150 × (70 − 25) = 67.5°C. Remaining thermal budget is 125°C − 67.5°C = 57.5°C, allowing ~0.38 W dissipation. Using V_CE(sat) ≈ 100 mV at 2 A, max I_C ≈ 3.8 A continuous under these conditions.

Can ZTX849STOA be used in avalanche mode?

No - ZTX849STOA is not rated or characterized for avalanche operation. Its V_(BR)CEO = 30 V is specified under open-base conditions only, and no SOA curves or energy ratings are provided for repetitive avalanche stress. Use with clamping diodes or snubbers is required for inductive load switching.

Is the ZTX849STOA pinout compatible with standard TO-92 footprints?

Yes - ZTX849STOA uses the E-Line TO-92 package (outline 3-291) with emitter-base-collector (E-B-C) pin order when viewed from the flat side with leads down. This matches JEDEC TO-92 mechanical standards and is compatible with automated insertion and wave soldering tooling calibrated for standard TO-92.

What is the minimum base current required to saturate ZTX849STOA at 5 A collector current?

Per datasheet test condition, saturation at I_C = 5 A requires I_B = 200 mA (I_C/I_B = 25). With h_FE ≥65 at this operating point, 77 mA would theoretically suffice, but 200 mA ensures deep saturation and margin against h_FE variation across temperature and unit-to-unit spread.