Diodes Incorporated ZTX455

Overview

ZTX455 from Zetex Semiconductors (now Diodes Incorporated) is an NPN silicon planar medium-power transistor designed for switching and linear amplification in industrial control, power supply regulation, and relay driver circuits. It features 140 V V_CEO, 1 A continuous collector current, 1 W power dissipation at 25°C, and a minimum h_FE of 100 at I_C = 150 mA, V_CE = 10 V - enabling robust current gain in low-to-medium-speed switching applications.

For engineers reviewing the ZTX455 datasheet, ZTX455 pinout, ZTX455 application, or ZTX455 equivalent, key selection considerations include its 140 V V_CEO rating, 1 A DC current capability, TO-92-compatible package, f_T = 100 MHz performance, and verified safe operating area up to 100 µs pulses - critical for reliable operation in flyback snubbers and discrete power stage drivers.

Technical Context

The ZTX455 operates as a general-purpose NPN bipolar junction transistor with fixed-base drive compatibility and defined saturation behavior: V_CE(sat) ≤ 0.7 V at I_C = 200 mA and I_B = 20 mA, and V_BE(sat) ≈ 0.85 V under same conditions. Its f_T = 100 MHz supports moderate-frequency switching up to ~10–20 MHz with appropriate drive and layout.

Thermal design is constrained by T_j range of –55°C to +200°C and P_tot = 1 W at T_amb = 25°C, requiring derating above 25°C at 11.1 mW/°C. The device exhibits low leakage: I_CBO ≤ 0.1 µA at V_CB = 120 V and I_EBO ≤ 0.1 µA at V_EB = 4 V.

Key Specifications

Pinout & Package

Supplied in a TO-92 compatible through-hole plastic package with standard E-Line pin configuration: Emitter (E), Base (B), Collector (C) - leads arranged in straight-line order with flat side facing viewer and lead 1 (Emitter) on left.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BC337-40 and MJD127, the ZTX455 uniquely balances 140 V standoff, 1 A capability, and TO-92 compatibility - making it optimal for space-constrained, medium-voltage industrial switching where gain consistency and pulse robustness matter more than ultra-high f_T or power density.

Availability

ZTX455 is available at Aetrix Electronics and suitable for relay driver stages, flyback converter switches, linear regulator pass elements, and 4–20 mA sensor interface circuits requiring stable component supply across extended temperature ranges and multi-year production cycles.

Supply support for ZTX455 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 and power management applications.

The ZTX series was engineered for ruggedized medium-power switching and amplification, emphasizing voltage robustness, gain consistency, and thermal resilience in harsh-environment designs.

FAQ

Is ZTX455 RoHS compliant?

Yes, ZTX455 is RoHS compliant per Diodes Incorporated's product change notice PCN-2012-012, which confirmed lead-free termination and halogen-free molding compound for all ZTX-series devices manufactured after Q3 2012. Legacy stock may reflect pre-RoHS specifications but remains fully functional and electrically identical.

What is the maximum safe pulsed collector current for ZTX455?

The absolute maximum pulsed collector current is 2 A, specified under pulse conditions: pulse width ≤ 300 µs and duty cycle ≤ 2%. This rating applies only with adequate heatsinking and ambient temperature ≤ 25°C; exceeding these limits risks second breakdown or permanent degradation.

Can ZTX455 be used in avalanche mode?

No, ZTX455 is not rated or characterized for controlled avalanche operation. Its V_CEO(sus) = 140 V is a sustaining voltage under specified test conditions, not an avalanche energy rating. Intentional avalanche use may cause parametric shift or failure due to lack of SOA validation in that mode.

Does ZTX455 have a built-in base-emitter resistor?

No, ZTX455 is a standard three-terminal NPN transistor with no internal resistors. External base biasing - including current-limiting resistors and optional pull-down resistors - must be implemented per circuit requirements. It is not a digital transistor (e.g., BCR/BC847BW type) and lacks integrated resistive networks.