Diodes Incorporated ZTX789ASTZ

Overview

ZTX789ASTZ from Diodes Incorporated is a PNP silicon planar medium-power high-gain bipolar junction transistor (BJT) with V_CEO = –25 V, h_FE = 200 at I_C = –2 A, and V_CE(sat) = –0.45 V at I_C = –2 A / I_B = –20 mA, designed for Darlington pair drivers and motor control stages in battery-powered industrial equipment.

For engineers reviewing the ZTX789ASTZ datasheet, ZTX789ASTZ pinout, ZTX789ASTZ application, or ZTX789ASTZ equivalent, key selection criteria include verified saturation voltage under high-current switching, thermal resistance (R_th(j-amb) = 116 °C/W on 1-in² PCB), and guaranteed h_FE ≥ 100 at I_C = –6 A for robust base drive design.

Technical Context

This PNP BJT operates in linear amplification and saturated switching modes, supporting DC and pulsed collector currents up to –8 A (peak) with f_T = 100 MHz at I_C = –50 mA, enabling use in medium-speed switching applications such as H-bridge half-bridges and relay drivers.

Its low V_CE(sat) (–0.25 V min at I_C = –1 A / I_B = –10 mA) and high h_FE (up to 800 at I_C = –10 mA) reduce base drive power and conduction losses, while R_th(j-case) = 70 °C/W supports direct mounting on copper-clad PCBs without heatsinks for ≤1.5 W continuous dissipation.

Key Specifications

Pinout & Package

Package: TO-92 (E-Line compatible, 3-lead plastic case). Mounting requires minimum 1-inch² copper area on PCB for rated power dissipation.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ZTX789ASTZ, ZTX753STZ trades lower saturation loss for higher voltage rating, while MJD2955T4G sacrifices switching speed and gain for vastly higher power capacity-making ZTX789ASTZ optimal for space-constrained, battery-powered 24 V systems needing fast, efficient medium-current switching.

Availability

ZTX789ASTZ is available at Aetrix Electronics and suitable for automotive window lift control, portable power tool motor drivers, and industrial relay driver stages requiring stable component supply across extended production lifecycles.

Supply support for ZTX789ASTZ 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 devices for power management, signal integrity, and connectivity applications.

ZTX789ASTZ belongs to the ZTX series of high-gain silicon BJTs engineered for medium-power linear and switching applications in cost-sensitive industrial and consumer systems where TO-92 footprint and thermal efficiency are critical.

FAQ

What is the maximum continuous collector current for ZTX789ASTZ?

The maximum continuous collector current is –3 A at T_amb = 25 °C with 1-inch² copper PCB area. Derating applies above 25 °C at 5.7 mW/°C, limiting usable current to ~1.8 A at 85 °C ambient. This rating assumes no heatsink and standard FR-4 board construction.

Can ZTX789ASTZ replace a Darlington pair in existing designs?

Yes-its h_FE ≥ 200 at –2 A enables single-transistor replacement of many Darlington configurations, reducing component count and base drive complexity. However, verify that V_CE(sat) ≤ –0.45 V meets your load's voltage headroom requirements, as Darlington pairs typically exhibit higher saturation voltage.

What is the recommended PCB layout for thermal performance?

Mount ZTX789ASTZ on a minimum 1-inch² copper pour connected directly to the emitter pad, with thermal vias beneath the pad if multilayer. Avoid routing high-current traces near the transistor body. The datasheet specifies this copper area achieves R_th(j-amb) = 116 °C/W, enabling full 1.5 W dissipation at 25 °C ambient.

Does ZTX789ASTZ support pulsed operation beyond its DC ratings?

Yes-peak pulse current is rated at –8 A with pulse width ≤300 µs and duty cycle ≤2%. Under these conditions, junction temperature rise remains within safe limits even with minimal copper area. Ensure gate/base drive circuitry can source/sink the required peak base current (e.g., –100 mA for –3 A collector pulse).