Diodes Incorporated ZTX849STZ

Overview

ZTX849STZ from Diodes Incorporated is an NPN silicon planar medium-power high-current transistor rated for 5 A continuous collector current, 30 V V_CEO, and 1.2 W power dissipation at 25°C ambient; it features low V_CE(sat) (≤220 mV at 5 A/200 mA drive) and supports fast switching (t_on/t_off = 45/630 ns), widely used in LCD backlight converters and battery-powered motor drivers.

For engineers reviewing the ZTX849STZ datasheet, ZTX849STZ pinout, ZTX849STZ application, or ZTX849STZ equivalent, key selection criteria include verified DC current gain (h_FE ≥100 at 5 A), thermal resistance (R_th(j-amb) = 150 °C/W), saturation voltage behavior under pulsed load, and TO-92-compatible mechanical fit for space-constrained PCB layouts.

Technical Context

This device operates as a medium-power NPN bipolar junction transistor with a maximum V_CEO of 30 V and V_CBO of 80 V, enabling use in step-up DC-DC converter switches where breakdown margin and safe operating area (SOA) are critical. Its h_FE remains ≥100 up to 5 A (IC=5 A, V_CE=1 V), supporting stable current amplification in linear and switching modes.

Designed for pulsed operation (duty cycle ≤2%, pulse width = 300 µs), it delivers 20 A peak current capability with low V_CE(sat) (200 mV typical at IC=5 A, IB=200 mA) and f_T = 100 MHz, making it suitable for high-efficiency, high-frequency switching in portable power stages.

Key Specifications

Pinout & Package

Package: TO-92 (E-Line compatible), through-hole, 3-pin plastic case with standard C-B-E terminal layout (viewed from flat side, leads down: Emitter–Base–Collector left-to-right).

Key Features

Applications

Equivalent & Alternatives

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

Compared with ZTX849STZ, ZTX851 trades current-handling linearity for higher voltage tolerance, while BCP56-10 sacrifices peak current capability for SMT manufacturability and improved thermal resistance-selection depends on whether board space, voltage margin, or current density dominates the design constraint.

Availability

ZTX849STZ is available at Aetrix Electronics and suitable for LCD backlight converters, flash gun discharge circuits, and battery-powered motor drivers requiring stable component supply across production lifecycles.

Supply support for ZTX849STZ 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 solutions for power management, signal integrity, and connectivity applications.

ZTX849STZ belongs to the ZTX series of high-current bipolar transistors designed specifically for cost-sensitive, high-reliability switching in portable and battery-operated power conversion systems.

FAQ

What is the maximum safe continuous collector current for ZTX849STZ at 70°C ambient?

At 70°C ambient, the practical continuous collector current is reduced to approximately 3.2 A due to thermal derating. With R_th(j-amb) = 150 °C/W and T_j(max) = 200°C, the allowable power dissipation drops to 0.87 W, limiting I_C based on V_CE(sat) ≈ 180 mV at that current level. PCB copper area and airflow significantly affect actual performance.

Can ZTX849STZ be used in linear amplifier configurations?

Yes, ZTX849STZ supports linear operation with h_FE ≥100 at I_C = 5 A and V_CE = 1 V, and its SOA curve permits DC operation up to 1.2 W at 25°C. However, thermal management is critical-linear use requires heatsinking or forced cooling above ~0.5 W dissipation to avoid junction overheating.

Is ZTX849STZ pin-compatible with standard TO-92 transistors like PN2222A?

No-ZTX849STZ uses E-B-C pinout (Emitter–Base–Collector left-to-right when viewed from flat side, leads down), whereas PN2222A uses E-C-B. Swapping them without board modification causes immediate circuit failure. Always verify pin order using the device marking and orientation diagram before substitution.

What is the recommended base drive for switching ZTX849STZ at 5 A collector current?

A base current of 200 mA is specified for full saturation at I_C = 5 A, implying a minimum base drive capability of 200 mA with <100 ns rise/fall times. Use a low-impedance driver (e.g., TC4427 or discrete MOSFET buffer) and keep base trace short to minimize inductance and prevent oscillation during switching transitions.