Diodes Incorporated ZTX614STOA

Overview

ZTX614STOA from Diodes Incorporated is an NPN silicon planar medium-power Darlington transistor with V_CEO = 100 V, I_C = 800 mA continuous, h_FE = 10,000 at I_C = 500 mA, P_tot = 1.0 W, and TO-92 compatible E-line package. It serves as a high-gain switching or linear amplification device in industrial control interfaces and relay drivers.

For engineers reviewing the ZTX614STOA datasheet, ZTX614STOA pinout, ZTX614STOA application, or ZTX614STOA equivalent, key selection criteria include verified Darlington gain linearity at 500 mA, V_CE(sat) ≤ 1.25 V under pulsed 800 mA drive, thermal derating slope of 5.7 mW/°C, and E-line TO-92 mechanical compatibility with BCX38 footprint.

Technical Context

This Darlington pair integrates two NPN transistors monolithically to deliver high DC current gain while maintaining single-base control. Its V_CEO(sus) = 100 V and V_CB0 = 120 V support robust blocking in inductive load switching, and the 1.25 V V_CE(sat) at I_C = 800 mA / I_B = 8 mA enables low-loss saturation in medium-power driver stages.

The device operates across –55 °C to +200 °C junction temperature range and features 100 nA I_CBO at V_CB = 60 V and 100 nA I_EBO at V_EB = 8 V - confirming tight leakage control for stable biasing in precision analog or safety-critical on/off circuits.

Key Specifications

Pinout & Package

Supplied in E-line TO-92 compatible package (ZTX614 3-215), with standard lead configuration: Emitter (E), Base (B), Collector (C) - leads arranged left-to-right as C–B–E when viewing flat side with leads down.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar NPN Darlington switching applications.

Compared with BCX38 and ZTX613, ZTX614STOA delivers the lowest V_CE(sat) among E-line TO-92 Darlington NPNs, enabling higher efficiency in thermally constrained relay and motor driver PCB layouts without changing footprint or thermal pad design.

Availability

ZTX614STOA is available at Aetrix Electronics and suitable for industrial relay drivers, DC motor controllers, LED array switches, and overvoltage protection circuits requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for ZTX614STOA 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 semiconductor company specializing in discrete, analog, and mixed-signal devices for industrial, computing, consumer, and communications markets.

ZTX614STOA belongs to the ZTX series of high-gain Darlington transistors designed specifically for medium-power switching in space-constrained industrial control and power interface applications.

FAQ

What is the maximum safe continuous collector current for ZTX614STOA at 75°C ambient?

At T_amb = 75 °C, derating applies: 1.0 W – (5.7 mW/°C × 50 °C) = 0.715 W max dissipation. With V_CE(sat) ≈ 1.25 V, I_C ≤ 0.715 W / 1.25 V = 572 mA. This ensures junction temperature remains below 200 °C under steady-state conditions with adequate PCB copper area.

Can ZTX614STOA replace BCX38 in existing PCBs without layout changes?

Yes - ZTX614STOA uses the identical E-line TO-92 package (ZTX614 3-215) and C–B–E pinout as BCX38. No PCB modification is required. Electrical improvements include lower V_CE(sat) (1.25 V vs. 1.5 V) and guaranteed h_FE ≥ 5000 at 100 mA, enhancing drive margin in aging designs.

Is pulse testing required to achieve the 10,000 h_FE specification?

Yes - the 10,000 h_FE value is measured under pulsed conditions (300 µs pulse width, ≤2% duty cycle) at I_C = 500 mA. In DC operation, h_FE remains ≥5000 at I_C = 100 mA and drops gradually with increasing I_C; design margins should use the 500 mA pulsed value only for transient load handling.

Does ZTX614STOA require a base-emitter resistor for stability?

Yes - a 10 kΩ resistor from base to emitter is recommended to prevent spurious turn-on due to leakage or noise, especially in high-temperature or high-humidity environments. This resistor does not significantly impact switching speed given the Darlington's high input impedance and 8 mA required base drive.