Diodes Incorporated ZTX614STOB

Overview

ZTX614STOB from Diodes Incorporated is an NPN silicon planar medium-power Darlington transistor with V_CEO = 100 V, I_C = 800 mA continuous, h_FE = 5000–10000 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 ZTX614STOB datasheet, ZTX614STOB pinout, ZTX614STOB application, or ZTX614STOB equivalent, key selection criteria include verified Darlington gain linearity at 500 mA, V_CE(sat) ≤ 1.25 V under 8 mA base 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 achieve high DC current gain while maintaining single-base control. Its V_CEO(sus) = 100 V and V_CBO = 120 V support operation in inductive load switching with flyback margin. The device is rated for T_j up to +200°C, enabling use in thermally constrained industrial enclosures.

Electrical testing follows pulsed conditions (300 µs width, ≤2% duty cycle) for h_FE, V_CE(sat), and V_BE(on) - critical for accurate thermal modeling in sustained conduction. The E-line TO-92 outline ensures mechanical drop-in replacement for legacy BCX38 designs without PCB rework.

Key Specifications

Pinout & Package

E-line TO-92 package: molded plastic case with 3 leads, JEDEC TO-92 outline compliant, lead finish matte tin, RoHS-compliant, footprint identical to BCX38.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BCX38 and ZTX613, ZTX614STOB delivers superior combination of 100 V blocking, 800 mA current capability, and guaranteed h_FE ≥ 5000 at 500 mA - making it optimal for space-constrained industrial switches needing robust flyback handling and logic-level drive.

Availability

ZTX614STOB is available at Aetrix Electronics and suitable for industrial relay drivers, DC motor controllers, LED array switches, and high-temperature sensor interfaces requiring stable component supply across extended temperature ranges.

Supply support for ZTX614STOB 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, headquartered in Plano, Texas, with design centers across Asia and manufacturing in China, Taiwan, and the Philippines.

ZTX614STOB belongs to the ZTX series of high-voltage, medium-power bipolar transistors designed specifically for industrial control, power switching, and ruggedized analog signal conditioning applications.

FAQ

What is the maximum safe continuous collector current for ZTX614STOB at 75°C ambient?

At T_amb = 75°C, derating from 25°C gives ΔT = 50°C; total derating = 50 × 5.7 mW = 285 mW. Remaining power = 1000 − 285 = 715 mW. With V_CE(sat) ≈ 1.25 V, max I_C = 715 mW / 1.25 V ≈ 572 mA. This is the practical continuous limit under natural convection.

Can ZTX614STOB replace BCX38 in existing PCBs without modification?

Yes - ZTX614STOB uses the identical E-line TO-92 mechanical outline and pinout (C-B-E), with same lead spacing and body dimensions. Electrical differences (higher V_CEO, higher h_FE) are backward-compatible; no layout change is required for drop-in substitution.

Is ZTX614STOB suitable for linear amplifier applications?

Yes - its specified h_FE linearity across I_C = 100–500 mA, low V_CE(sat), and ±10 V V_EB rating support Class-A and AB amplifier stages. Thermal stability up to +200°C junction temperature enables reliable operation in uncooled analog front-ends.

Does ZTX614STOB require a base resistor when driven by a 3.3 V MCU GPIO?

Yes - although h_FE is high, a base resistor is mandatory to limit I_B and prevent thermal runaway. For 800 mA I_C, target I_B = 8 mA; with 3.3 V GPIO and V_BE(on) ≈ 1.8 V, R_B = (3.3 − 1.8) V / 8 mA ≈ 188 Ω (use 180 Ω standard value).