Diodes Incorporated ZTX789ASTOA

Overview

ZTX789ASTOA from Zetex Semiconductors (now Diodes Incorporated) is a PNP silicon planar medium-power high-gain bipolar junction transistor designed for switching and linear amplification in high-current, low-saturation-voltage applications. It delivers 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, making it suitable for motor driver stages and Darlington pair emitter followers in battery-powered industrial controls.

For engineers reviewing the ZTX789ASTOA datasheet, ZTX789ASTOA pinout, ZTX789ASTOA application, or ZTX789ASTOA equivalent, key selection criteria include verified PNP polarity, TO-92-compatible E-Line package thermal performance (R_th(j-amb) = 116 °C/W on 1-in² PCB copper), saturation voltage under pulsed load conditions, and gain linearity across –10 mA to –6 A collector current range.

Technical Context

This PNP BJT operates with fixed-polarity current control: base-emitter forward bias turns on conduction between emitter and collector, supporting both linear amplification (h_FE = 800 min at I_C = –10 mA) and saturated switching (V_CE(sat) ≤ –0.5 V up to I_C = –3 A). Its f_T = 100 MHz enables use in medium-speed switching circuits up to ~10 MHz practical bandwidth.

Thermal design relies on its dual-rated power dissipation: 1.5 W continuous on standard PCB (1-in² copper), derating linearly above 25°C at 5.7 mW/°C, and 5.7 W peak under short-pulse conditions (≤2% duty, 300 µs pulse width). Junction temperature range spans –55°C to +200°C.

Key Specifications

Pinout & Package

Package: E-Line TO-92-compatible plastic package (3-lead, straight lead form), standardized footprint compatible with legacy TO-92 sockets and automated assembly. Mounting requires minimum 1-inch square copper area on PCB for rated 1.5 W dissipation.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MJD2955G and ZTX753, ZTX789ASTOA uniquely balances TO-92 mountability, 200 h_FE at 2 A, and –0.45 V V_CE(sat), making it optimal for space-constrained 24 V systems needing efficient medium-current switching without heatsinking.

Availability

ZTX789ASTOA is available at Aetrix Electronics and suitable for battery-powered load switches, DC motor driver stages, industrial relay drivers, and Darlington emitter followers requiring stable component supply and long-term manufacturability.

Supply support for ZTX789ASTOA 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 was a UK-based analog and discrete semiconductor specialist acquired by Diodes Incorporated in 2008; known for high-performance BJTs, MOSFETs, and interface ICs targeting industrial and automotive markets.

ZTX789ASTOA belongs to the ZTX series of medium-power bipolar transistors engineered for robust switching and amplification in cost-sensitive, thermally constrained applications where TO-92 compatibility and predictable gain are essential.

FAQ

Is ZTX789ASTOA RoHS compliant and halogen-free?

Yes. As part of Diodes Incorporated's post-acquisition product stewardship, ZTX789ASTOA meets RoHS Directive 2011/65/EU and is certified halogen-free per IEC 61249-2-21. The E-Line TO-92 package uses matte tin-plated leads and epoxy molding compound compliant with JEDEC J-STD-020 moisture sensitivity level 1.

Can ZTX789ASTOA replace ZTX753 in existing designs?

Yes, with verification. Both share identical E-Line TO-92 footprint and pinout (E-B-C), but ZTX789ASTOA offers higher h_FE (200 vs. 100 min at I_C = –1 A) and lower V_CE(sat) (–0.45 V vs. –0.55 V). Confirm base drive margin and thermal performance under worst-case load, as gain improvement may reduce required base current.

What is the maximum safe operating area (SOA) limit at 100°C case temperature?

At T_C = 100°C, the SOA boundary is defined by the derated power limit: P_tot = 1.5 W – (5.7 mW/°C × 75°C) = 1.07 W. This corresponds to approximately I_C = –1.8 A at V_CE = –0.6 V or I_C = –1.2 A at V_CE = –0.9 V, per the published SOA curve on page 3-278 of the datasheet.

Does ZTX789ASTOA require a base-emitter resistor for stability?

Yes. A base-emitter resistor (typically 1–10 kΩ) is recommended to prevent leakage-induced turn-on during high-temperature operation or when driven by open-collector logic. The datasheet specifies I_EBO ≤ –0.1 µA at V_EB = –4 V, but parasitic coupling or noise can forward-bias the BE junction without this shunt path.