Diodes Incorporated ZTX949

Overview

ZTX949 from Zetex Semiconductors (now Diodes Incorporated) is a PNP silicon planar medium-power high-current transistor designed for switching and linear amplification in industrial power control circuits. It delivers -4.5 A continuous collector current, -20 A peak pulse current, and V_CE(sat) as low as -60 mV at -5 A / -300 mA drive, with h_FE = 100–300 across 10 mA to 20 A, and operates reliably from -55°C to +200°C junction temperature.

For engineers reviewing the ZTX949 datasheet, ZTX949 pinout, ZTX949 application, or ZTX949 equivalent, key selection criteria include its low saturation voltage under high-current switching, exceptional gain linearity down to 10 mA, thermal robustness up to +200°C, and TO-92-compatible E-Line package suitability for space-constrained PCB layouts in motor drivers and SMPS feedback stages.

Technical Context

The ZTX949 is a discrete PNP bipolar junction transistor optimized for high-current switching with minimal conduction loss. Its V_CE(sat) remains below -100 mV up to -2 A and -160 mV at -5 A, while h_FE maintains ≥100 from IC = -10 mA to -5 A under V_CE = -1 V, supporting stable biasing across wide load ranges.

Thermally, it features R_th(j-amb) = 150°C/W (PCB-mounted, 1-inch² copper) and R_th(j-case) = 50°C/W, enabling operation at T_j = +200°C with appropriate heatsinking. Its f_T = 100 MHz and C_obo = 122 pF support fast switching in <130 ns turn-off time under -4 A load conditions.

Key Specifications

Pinout & Package

Package: E-Line TO-92 compatible (3-312 outline), epoxy-molded, through-hole mounting. Pin identification is standardized per JEDEC TO-92: Emitter (E), Base (B), Collector (C) - left-to-right when viewing flat side with leads downward.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MJD2955 and ZTX951, the ZTX949 uniquely balances TO-92 form factor, -4.5 A continuous rating, and sub-100 mV saturation voltage - making it optimal for space-constrained, thermally sensitive 24 V industrial controls where both efficiency and footprint matter.

Availability

ZTX949 is available at Aetrix Electronics and suitable for motor drive stages, SMPS feedback amplifiers, industrial solenoid drivers, and overcurrent protection sensors requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for ZTX949 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

Zetex Semiconductors, now part of Diodes Incorporated, specializes in high-performance discrete semiconductors for power management and signal conditioning in harsh-environment applications.

The ZTX series was developed specifically for industrial and automotive power switching where reliability at elevated temperatures and consistent gain linearity are critical design requirements.

FAQ

What is the maximum safe operating temperature for ZTX949?

The ZTX949 has a specified junction temperature range of -55°C to +200°C. Its thermal resistance junction-to-ambient is 150°C/W on a 1-inch² copper pad, so sustained operation at +200°C requires careful PCB layout and limited power dissipation. Derating curves show usable power drops to ~0.4 W at +100°C ambient.

Can ZTX949 be used in linear amplifier mode?

Yes - its h_FE remains stable from 10 mA to 20 A, and V_CE(sat) is well-characterized across current levels. The device supports Class-A and Class-AB operation with predictable bias points, though thermal management is essential above 1 W dissipation due to R_th(j-amb) = 150°C/W.

Is ZTX949 RoHS compliant and halogen-free?

Yes - Diodes Incorporated confirms ZTX949 meets RoHS Directive 2011/65/EU and is halogen-free per IEC 61249-2-21. The device carries the "Green" designation in official Diodes product documentation and is supplied in lead-free, matte-tin-plated leads.

Does ZTX949 require a base resistor in switching applications?

Yes - base current must be externally limited to avoid damage. For -5 A collector current with h_FE ≈ 100, ~50 mA base drive is required. A 100 Ω resistor from a 5 V logic source provides ~45 mA, ensuring saturation while preventing excessive base dissipation and secondary breakdown risk.