Diodes Incorporated ZTX790A

Overview

ZTX790A from Zetex Semiconductors (now Diodes Incorporated) is a PNP silicon planar medium-power high-gain transistor in TO-92 package, rated for -40 V V_CEO, -2 A continuous collector current, and 200 minimum h_FE at I_C = -1 A; used in siren drivers, Darlington pairs, and battery-powered motor control circuits.

For engineers reviewing the ZTX790A datasheet, ZTX790A pinout, ZTX790A application, or ZTX790A equivalent, key selection criteria include verified PNP switching performance at -1 A/−2 A, low V_CE(sat) down to −0.25 V, thermal resistance of 116 °C/W on PCB, and compatibility with E-Line TO-92 footprint.

Technical Context

This device operates as a medium-power PNP bipolar junction transistor optimized for linear amplification and saturated switching. It delivers h_FE = 200–800 across I_C = -10 mA to -2 A and maintains V_CE(sat) ≤ -0.45 V at I_C = -1 A / I_B = -10 mA.

Its f_T = 100 MHz at I_C = -50 mA enables use in audio-frequency switching and pulse applications. Thermal design is supported by R_th(j-amb) = 116 °C/W on 1-inch² copper PCB, with safe operating area validated up to +175 °C junction temperature.

Key Specifications

Pinout & Package

Package: TO-92 (E-Line compatible), 3-lead through-hole plastic package with standard C-B-E pin assignment (viewed from flat side, leads down).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MJD2955 and BC557B, ZTX790A uniquely balances TO-92 mountability, -2 A current handling, 100 MHz f_T, and sub-0.5 V V_CE(sat)-making it optimal for compact, battery-fed, medium-speed switching where thermal mass and board space are constrained.

Availability

ZTX790A is available at Aetrix Electronics and suitable for siren driver circuits, Darlington pair configurations, and battery-powered motor control applications requiring stable component supply and long-term obsolescence management.

Supply support for ZTX790A 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, acquired by Diodes Incorporated in 2008, specialized in high-performance discrete semiconductors for power management and signal conditioning.

ZTX790A belongs to the ZTX series of medium-power bipolar transistors designed specifically for robust, cost-effective switching and amplification in industrial and consumer power electronics.

FAQ

What is the maximum safe continuous collector current for ZTX790A?

The ZTX790A supports -2 A continuous collector current at T_amb = 25 °C when mounted on a PCB with ≥1 inch² copper area. Derating is required above 25 °C at 5.7 mW/°C, limiting usable current in high-temperature environments unless additional thermal management is applied.

Can ZTX790A be used in linear amplifier mode?

Yes-ZTX790A is characterized for linear operation with h_FE = 250–800 across I_C = -10 mA to -2 A and V_CE = -2 V. Its f_T = 100 MHz and low distortion at moderate signal levels make it suitable for Class-A audio preamplifiers and sensor interface stages.

Is ZTX790A pin-compatible with BC557 or BC639?

No-ZTX790A uses E-Line TO-92 pinout (Emitter-Base-Collector, left-to-right viewed from flat side), while BC557 is C-B-E and BC639 is C-E-B. Mechanical compatibility does not imply electrical or functional interchangeability; pin mapping must be verified per schematic layout.

What is the recommended PCB layout for thermal performance?

For optimal thermal performance, mount ZTX790A on a minimum 1-inch² copper pour connected directly to the emitter pad. Avoid thermal isolation; use multiple vias under the pad if internal layers are used. The datasheet specifies R_th(j-amb) = 116 °C/W assumes this copper area and no conformal coating.