Diodes Incorporated ZTX553

Overview

ZTX553 from Zetex Semiconductors (now Diodes Incorporated) is a PNP silicon planar medium-power bipolar junction transistor rated for -100 V V_CEO, -1 A continuous collector current, and 1 W power dissipation at 25°C ambient-designed for high-voltage switching and linear amplification in industrial power supplies and relay drivers.

For engineers reviewing the ZTX553 datasheet, ZTX553 pinout, ZTX553 application, or ZTX553 equivalent, key selection factors include verified V_CEO(sus) = -100 V, h_FE = 40–200 at I_C = -150 mA, f_T = 150 MHz, V_CE(sat) = -0.25 V @ I_C = -150 mA/I_B = -15 mA, and TO-92 package compatibility with E-Line footprint.

Technical Context

The ZTX553 operates as a medium-power PNP BJT with fully specified breakdown limits: V_CBO = -120 V, V_CEO(sus) = -100 V, and V_EBO = -5 V. Its DC current gain spans 40–200 across two test conditions (I_C = -150 mA and -1 A), supporting both saturated switching and analog amplification roles.

With f_T = 150 MHz at I_C = -50 mA/V_CE = -10 V, it delivers usable RF performance up to VHF band; C_obo = 12 pF at V_CB = -10 V confirms low output capacitance for fast turn-off. Pulse-tested parameters (300 µs, ≤2% duty cycle) ensure reliability under transient load conditions.

Key Specifications

Pinout & Package

Supplied in an E-Line TO-92 compatible plastic package (3-lead, straight lead form), with standard pin assignment: Emitter (E), Base (B), Collector (C) - leads arranged left-to-right as viewed from flat side with 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 ZTX550, the ZTX553 uniquely balances 100 V blocking, TO-92 usability, and 150 MHz bandwidth-making it optimal for space-constrained, high-voltage industrial controls where thermal mass is limited and signal integrity matters.

Availability

ZTX553 is available at Aetrix Electronics and suitable for industrial relay drivers, DC-DC auxiliary supplies, linear voltage regulators, and high-voltage signal amplifiers requiring stable component supply and long-term obsolescence management.

Supply support for ZTX553 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 industrial, automotive, and power management applications.

The ZTX series was engineered for robust medium-power switching and amplification in harsh environments, emphasizing high-voltage tolerance, gain consistency, and TO-92 reliability across temperature extremes.

FAQ

What is the maximum safe operating voltage for ZTX553 in a switching application?

The ZTX553 is rated for V_CEO(sus) = -100 V under pulsed conditions and V_CEO = -100 V absolute maximum. For reliable long-term operation, apply ≤80 V in DC or repetitive switching to maintain 20% voltage margin against transients and temperature drift.

Can ZTX553 replace ZTX552 in existing designs?

Yes-ZTX553 is a direct upgrade of ZTX552 with identical pinout, package, and biasing, but offers improved V_CBO (-120 V vs. -100 V) and V_CEO(sus) (-100 V vs. -80 V). No layout or schematic changes are required; verify system voltage headroom exceeds 80 V.

What is the recommended base drive for saturation switching?

For guaranteed saturation at I_C = -1 A, apply I_B ≥ -100 mA (h_FE min = 10 at this condition). At I_C = -150 mA, I_B = -15 mA suffices per datasheet test condition; use 2× that for margin in production designs.

Does ZTX553 require a heatsink in 1 W continuous operation?

At 1 W dissipation and T_amb = 25°C, the TO-92 package reaches ~150°C junction temperature-exceeding safe limits. Derate to ≤500 mW without heatsink; for full 1 W, use minimum 10 cm² copper pour or clip-on heatsink to hold T_j ≤150°C.