Diodes Incorporated ZTX953STZ

Overview

ZTX953STZ 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 −3.5 A continuous collector current, −10 A peak pulse current, and exhibits very low saturation voltage (−140 mV at IC = −2 A, IB = −200 mA), with DC current gain hFE ≥ 100 at IC = −10 mA and ≥ 50 at IC = −4 A.

For engineers reviewing the ZTX953STZ datasheet, ZTX953STZ pinout, ZTX953STZ application, or ZTX953STZ equivalent, key selection criteria include its −100 V VCEO rating, −1.2 W power dissipation at 25°C ambient, TO-92 compatible E-Line package, low VCE(sat) performance under high-current drive, and suitability for pulsed-load switching in relay drivers and motor control stages.

Technical Context

The ZTX953STZ is a medium-power PNP bipolar junction transistor optimized for high-current switching with low on-state loss. Its structure supports stable gain up to −10 A (hFE ≥ 15 at IC = −10 A), and it features a −140 V VCBO rating enabling use in inductive load circuits with significant back-EMF.

Thermal design is supported by Rth(j-amb) = 150 °C/W (PCB-mounted, 1-inch² copper) and Rth(j-case) = 50 °C/W, with safe operating area validated for single-pulse and DC conditions across −55°C to +175°C junction temperature range.

Key Specifications

Pinout & Package

Package: E-Line TO-92 compatible (3-318 outline), plastic molded, through-hole mounting. Dimensions and lead spacing conform to JEDEC TO-92 mechanical standard.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ZTX953STZ, ZTX951STZ trades voltage/current headroom for smaller thermal footprint, while MJD2955G offers greater power handling at the cost of board space, assembly complexity, and lack of TO-92 compatibility.

Availability

ZTX953STZ is available at Aetrix Electronics and suitable for relay driver stages, DC motor direction control, solenoid power switching, and industrial PLC output modules requiring stable component supply and long-term obsolescence management.

Supply support for ZTX953STZ 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 markets.

The ZTX series targets medium-power discrete switching applications, emphasizing ruggedness, consistent gain at high current, and compatibility with legacy through-hole manufacturing infrastructure.

FAQ

What is the maximum safe continuous collector current for ZTX953STZ at 75°C ambient?

At Tamb = 75°C, derating applies: Ptot = 1.2 W × (1 − (75 − 25)/150) = 0.8 W. Using VCE(sat) ≈ −140 mV at −2 A, max continuous IC is ~5.7 A thermally, but absolute rating remains −3.5 A per datasheet. Therefore, −3.5 A is the hard limit regardless of cooling.

Can ZTX953STZ be used in avalanche mode?

No - ZTX953STZ is not rated or characterized for controlled avalanche operation. Its V(BR)CEO = −100 V is a breakdown limit, not an energy-rated avalanche specification. Operation beyond VCEO risks irreversible junction failure.

Is a base resistor required when driving ZTX953STZ from a 3.3 V microcontroller GPIO?

Yes - a series base resistor is mandatory. With VBE(sat) ≈ −960 mV and typical hFE ≈ 100 at −10 mA, a 3.3 V GPIO must sink ~10 mA base current. A 220 Ω resistor limits IB to ~10.5 mA, ensuring saturation while staying within GPIO drive capability.

Does ZTX953STZ have built-in ESD protection?

No - the datasheet does not specify any on-chip ESD protection structures. External protection (e.g., series resistance + clamping diode) is recommended in handling and circuit design, especially in automated assembly or field-replaceable modules exposed to human contact.