Diodes Incorporated ZTX957

Overview

ZTX957 from Diodes Incorporated is a PNP silicon planar medium-power high-current transistor designed for switching and linear amplification in industrial power control circuits. It delivers -1 A continuous collector current, -300 V V_CEO, -140 mV V_CE(sat) at -1 A/-300 mA drive, and operates up to +200°C junction temperature - enabling robust performance in relay drivers, SMPS feedback stages, and high-voltage DC-DC converters.

For engineers reviewing the ZTX957 datasheet, ZTX957 pinout, ZTX957 application, or ZTX957 equivalent, key selection criteria include verified PNP high-voltage switching capability, low saturation voltage under 1 A load, thermal stability across -55°C to +200°C, and TO-92 package compatibility with legacy board layouts.

Technical Context

The ZTX957 is a discrete bipolar junction transistor optimized for medium-power PNP switching where high breakdown voltage and low on-state loss are critical. Its -300 V V_CEO rating and -140 mV V_CE(sat) at -1 A support reliable operation in flyback snubbers and inductive load drivers without external clamping.

It features a minimum h_FE of 100 at -1 A/-10 V and maintains usable gain (≥10) up to -2 A, with f_T = 85 MHz confirming suitability for moderate-speed switching (≤500 kHz). Thermal resistance R_th(j-amb) = 150°C/W reflects standard PCB mounting with ≥1 inch² copper.

Key Specifications

Pinout & Package

Package: TO-92 (E-Line compatible, 3-327 outline), through-hole, epoxy-molded plastic case with standard lead spacing and coplanarity for wave soldering.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ZTX951 and MJD2955, the ZTX957 uniquely balances -300 V blocking, -1 A current, and TO-92 form factor - making it the only option for space-constrained, high-voltage switching without heatsink or voltage derating.

Availability

ZTX957 is available at Aetrix Electronics and suitable for industrial power supplies, relay driver modules, and high-reliability DC-DC pre-regulators requiring stable component supply across extended temperature and voltage ranges.

Supply support for ZTX957 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 components for industrial, automotive, and computing applications.

The ZTX957 belongs to Diodes' legacy high-voltage bipolar transistor product line, engineered specifically for ruggedized switching in power conversion and control systems operating beyond standard commercial temperature limits.

FAQ

What is the maximum safe operating voltage for ZTX957 in continuous DC applications?

The ZTX957 is rated for -300 V V_CEO at T_j = 25°C, with derating to -200 V at +100°C junction temperature. For continuous DC use, apply ≤80% of rated V_CEO (i.e., ≤-240 V) with adequate PCB creepage and clearance per IPC-2221B Class B requirements.

Can ZTX957 replace ZTX953 in existing designs?

Yes - ZTX957 is a direct upgrade to ZTX953, offering identical TO-92 packaging, improved V_CEO (-300 V vs. -250 V), lower V_CE(sat) (-140 mV vs. -180 mV at -1 A), and extended T_j range (+200°C vs. +150°C), with no layout or bias changes required.

Is SPICE modeling supported for ZTX957?

Yes - Diodes Incorporated provides an industry-standard SPICE model for ZTX957 covering DC, AC, and transient behavior, including temperature-dependent parameters and parasitic capacitances. The model is validated against measured f_T, C_obo, and switching times.

What is the recommended base resistor value for saturation at 1 A collector current?

With h_FE ≥100 and V_BE(sat) ≈ -1 V at -1 A, a base current of ≥10 mA is required. Using a -5 V logic drive, a 470 Ω resistor delivers ~10.6 mA, ensuring robust saturation while limiting base power dissipation to <50 mW.