Diodes Incorporated ZTX758

Overview

ZTX758 from Diodes Incorporated is a 400V PNP medium-power high-voltage transistor in E-Line (TO-92 compatible) package, rated for -0.5A continuous collector current, -400V V_CEO, and 1W power dissipation at +25°C ambient. It operates up to +200°C junction temperature and features low saturation voltage of -250mV at -50mA/-5mA drive, supporting high-reliability industrial switching and flyback converter applications.

For engineers reviewing the ZTX758 datasheet, ZTX758 pinout, ZTX758 application, or ZTX758 equivalent, key selection criteria include its -400V breakdown rating, AEC-Q101 qualification, thermal resistance of 175°C/W (min pad layout), and verified pulse current capability of -1A - critical for snubber circuits, relay drivers, and HV DC-DC stage control.

Technical Context

The ZTX758 is a silicon PNP bipolar junction transistor optimized for high-voltage linear and switching operation. Its BV_CEO = -400V and BV_CBO = -400V enable use in off-line primary-side switching where high reverse blocking is mandatory. The device delivers h_FE = 50 at -1mA and drops to 40 at -200mA, indicating stable gain across mid-current range.

Thermal design is supported by dual R_θJA ratings: 116°C/W (25mm² copper pad) and 175°C/W (minimum pad), with R_θJL = 70°C/W confirming efficient heat conduction through the collector lead. f_T = 50MHz ensures usable bandwidth for moderate-speed switching above 10kHz.

Key Specifications

Pinout & Package

E-Line (TO-92 compatible) molded plastic package with matte tin-plated leads; 0.159g weight; UL 94V-0 flammability rating; flat face marking "ZTX758", rounded face showing "C E B" sequence.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ZTX753, ZTX758 provides 100V higher blocking and 67% higher continuous current in identical E-Line packaging; versus MJD2955, it trades raw power for compactness and high-voltage suitability - making ZTX758 optimal for space-constrained, off-line–capable designs.

Availability

ZTX758 is available at Aetrix Electronics and suitable for industrial relay drivers, off-line flyback controllers, high-voltage linear regulators, and capacitor discharge ignition systems requiring stable component supply and AEC-Q101 reliability assurance.

Supply support for ZTX758 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, headquartered in Plano, Texas, with design and manufacturing operations across Asia and the Americas.

The ZTX series targets high-reliability medium-power bipolar transistors for industrial, automotive, and appliance applications - emphasizing high-voltage tolerance, thermal resilience, and RoHS/Green compliance.

FAQ

What is the maximum safe operating voltage for ZTX758 in continuous DC applications?

The ZTX758 is rated for V_CEO = -400V and V_CBO = -400V under DC conditions at T_A = +25°C. For reliable long-term operation, design voltage stress should remain ≤80% of rating (-320V) with appropriate derating for temperature and transient margins per DS33299 Section 3.

Can ZTX758 be used as a direct replacement for ZTX757 in existing designs?

No - ZTX757 is an NPN transistor (V_CEO = +400V), while ZTX758 is PNP with complementary polarity and opposite pinout (C-E-B vs E-B-C). Swapping requires circuit rework including bias network inversion and layout revision to match E-Line pin assignment.

Does ZTX758 require a heatsink in a 1W switching application at +60°C ambient?

Yes - at +60°C ambient and 1W dissipation, junction temperature would reach ~235°C using R_θJA = 175°C/W, exceeding the +200°C limit. A minimal copper pour (≥25mm²) or clip-on heatsink reducing R_θJA to ≤110°C/W is required for safe operation.

Is ZTX758 suitable for Class B audio amplifier output stages?

No - its f_T = 50MHz and h_FE variation across current range make it unsuitable for linear audio amplification. It lacks specified linearity parameters (THD, SOA curves) and is optimized for switching, not analog fidelity; dedicated audio transistors like BD139/BD140 are recommended instead.