Diodes Incorporated ZTX549

Overview

ZTX549 from Diodes Incorporated is a PNP silicon planar medium-power transistor designed for linear amplification and switching in low-voltage DC-DC converter control stages, relay drivers, and LED current sinks. It features V_CEO = −30 V, I_C = −1 A continuous, P_tot = 1 W at T_amb = 25°C, h_FE = 100–300 at I_C = −500 mA, and f_T = 100 MHz - enabling robust operation in industrial power management circuits.

For engineers reviewing the ZTX549 datasheet, ZTX549 pinout, ZTX549 application, or ZTX549 equivalent, key selection criteria include verified PNP polarity, TO-92-compatible E-line package thermal derating (5.7 mW/°C above 25°C), safe operating area up to 100°C junction temperature, and confirmed V_CE(sat) ≤ −0.5 V at I_C = −1 A / I_B = −100 mA under pulsed conditions.

Technical Context

The ZTX549 operates as a medium-power PNP bipolar junction transistor with fixed emitter-base and collector-base breakdown limits (V_(BR)EBO = −5 V, V_(BR)CBO = −35 V) and specified saturation behavior across three current tiers: −50 mA, −500 mA, and −1 A. Its h_FE variation (100–300) is tightly correlated to I_C and V_CE, with guaranteed minimum gain of 70 at −50 mA and 40 at −1 A.

Switching performance is characterized by t_on = 300 ns and t_off = 50 ns under defined load (I_C = −500 mA, V_CC = −10 V, I_B1 = I_B2 = −50 mA), and C_obo = 25 pF at V_CB = −10 V, supporting stable operation in <100 MHz signal paths with predictable Miller capacitance effects.

Key Specifications

Pinout & Package

Package: TO-92-compatible E-line (3-lead, straight lead form, epoxy molded). Pin assignment follows standard PNP TO-92 orientation: viewed from flat side with leads down, left-to-right is Emitter (E), Base (B), Collector (C).

Key Features

Applications

Equivalent & Alternatives

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

Compared with ZTX549, ZTX550 offers higher voltage tolerance without sacrificing thermal performance, while BC807-40 trades power capability for miniaturization and gain consistency - making ZTX549 optimal for through-hole 1 A PNP switching where cost, reliability, and thermal headroom are prioritized over footprint size.

Availability

ZTX549 is available at Aetrix Electronics and suitable for industrial motor control interfaces, PLC output modules, and LED lighting drivers requiring stable component supply with long-term manufacturing continuity.

Supply support for ZTX549 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 centers across Asia and manufacturing in China, Taiwan, and Malaysia.

The ZTX series targets medium-power discrete bipolar transistors for industrial and automotive-qualified applications where proven reliability, wide temperature range (−55°C to +200°C), and consistent parametric distribution are essential.

FAQ

Is ZTX549 RoHS compliant and halogen-free?

Yes, ZTX549 meets RoHS Directive 2011/65/EU and is certified halogen-free per IEC 61249-2-21. The device uses lead-free matte tin plating on leads and complies with JEDEC J-STD-020 moisture sensitivity level 1 (MSL-1), allowing unlimited floor life at ≤30°C/85% RH.

What is the maximum junction temperature and how does it affect derating?

The ZTX549 has a maximum junction temperature (T_j) of +200°C. Power dissipation must be linearly derated above T_amb = 25°C at 5.7 mW/°C - meaning at 100°C ambient, maximum allowable P_tot drops to 659 mW. Thermal resistance R_θJA is 175°C/W in free-air TO-92 mounting.

Can ZTX549 be used in linear regulator pass elements?

Yes - its V_CEO = −30 V, I_C = −1 A, and SOA curve support use as a PNP pass transistor in adjustable negative linear regulators (e.g., LM337-based designs). Safe operation requires limiting V_CE × I_C to ≤1 W and ensuring case temperature remains below 150°C under worst-case load and dropout conditions.

Does ZTX549 have a documented SPICE model for simulation?

Yes, Diodes Incorporated provides a validated PSPICE model for ZTX549 (file: ZTX549.lib), including temperature-dependent β, V_BE, and capacitance parameters. The model reproduces measured h_FE, V_CE(sat), and f_T within ±8% across −55°C to +150°C, and is hosted in the manufacturer's official component library portal.