Diodes Incorporated ZTX789ASTOB

Overview

ZTX789ASTOB from Diodes Incorporated is a PNP silicon planar medium-power high-gain bipolar junction transistor with V_CEO = –25 V, h_FE = 200 at I_C = –2 A, and V_CE(sat) = –0.45 V (I_C = –2 A, I_B = –20 mA), designed for Darlington pair replacement and motor driver stages in battery-powered industrial control modules.

For engineers reviewing the ZTX789ASTOB datasheet, ZTX789ASTOB pinout, ZTX789ASTOB application, or ZTX789ASTOB 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 copper), and guaranteed gain linearity across –10 mA to –6 A collector current range.

Technical Context

This PNP BJT operates as a medium-power linear or switching amplifier with fixed-emitter bias topology. Its design supports DC-coupled Darlington configurations and handles pulsed peak currents up to –8 A, with f_T = 100 MHz enabling reliable operation in low-frequency power switching (≤100 kHz) and analog amplification below 10 MHz.

Thermal performance is defined for two mounting conditions: R_th(j-amb) = 175 °C/W (free-air) and 116 °C/W (1-in² PCB copper), and safe operating area (SOA) curves are validated from –55°C to +175°C junction temperature, supporting automotive under-hood and industrial motor-control environments.

Key Specifications

Pinout & Package

Package: TO-92 (E-Line compatible, 3-lead plastic case). Mounting requires minimum 1-inch² copper area 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 MJD2955T4G and ZTX753STOB, ZTX789ASTOB delivers optimal balance of gain, saturation voltage, and thermal performance in TO-92 for ≤25 V, ≤3 A switching-making it preferred for space-constrained, battery-operated motor and relay interfaces where efficiency and footprint are critical.

Availability

ZTX789ASTOB is available at Aetrix Electronics and suitable for brushed DC motor drivers, Darlington input stages, battery-powered sensor interfaces, and industrial relay drivers requiring stable component supply and long-term manufacturability.

Supply support for ZTX789ASTOB 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 power management, signal integrity, and protection devices for industrial and automotive markets.

ZTX789ASTOB belongs to the ZTX series of high-gain silicon transistors engineered specifically for medium-power linear amplification and switching in cost-sensitive, thermally constrained applications such as portable equipment and programmable logic controllers.

FAQ

What is the maximum continuous collector current for ZTX789ASTOB?

The maximum continuous collector current is –3 A at T_amb = 25°C with 1-inch² PCB copper. Derating applies above 25°C at 5.7 mW/°C, reducing usable current to –1.8 A at 70°C ambient. This rating assumes no additional heatsinking and conforms to the practical power dissipation limit of 1.5 W.

Can ZTX789ASTOB replace a Darlington pair directly?

ZTX789ASTOB is explicitly positioned as a Darlington replacement due to its high h_FE (≥200 at –2 A) and low V_CE(sat), but it does not integrate a built-in diode or second transistor. It replaces the *output* transistor in a Darlington stage-requiring external base drive optimization-but cannot substitute the entire two-transistor assembly without circuit redesign.

Is ZTX789ASTOB suitable for automotive under-hood use?

Yes-its guaranteed operating junction temperature range of –55°C to +200°C, validated SOA up to –8 A peak pulse, and thermal resistance of 116 °C/W on standard PCB copper meet requirements for non-safety-critical under-hood functions like HVAC blower control and seat-motor drivers, provided board layout adheres to the 1-in² copper rule.

What is the typical transition frequency and its design implication?

The typical transition frequency f_T is 100 MHz at I_C = –50 mA and V_CE = –5 V. While not intended for RF use, this bandwidth ensures clean switching edges and minimal storage time in PWM-driven motor and relay applications up to 100 kHz, supporting fast turn-on/turn-off with predictable timing margins.