Diodes Incorporated ZTX651STOB

Overview

ZTX651STOB from Diodes Incorporated is an NPN silicon planar medium-power bipolar junction transistor rated for 60 V V_CEO, 2 A continuous collector current, and 1 W power dissipation at T_amb = 25°C, with low V_CE(sat) (0.12 V typ. at I_C = 1 A, I_B = 100 mA). It serves as a general-purpose switching and linear amplification device in industrial power supplies and motor drive stages.

For engineers reviewing the ZTX651STOB datasheet, ZTX651STOB pinout, ZTX651STOB application, or ZTX651STOB equivalent, key selection criteria include verified V_CEO = 60 V, I_C = 2 A continuous rating, thermal resistance R_th(j-amb) = 175 °C/W (free air), TO-92-compatible E-Line package, and documented f_T = 175 MHz performance under specified bias conditions.

Technical Context

The ZTX651STOB operates as a medium-power NPN BJT optimized for DC and pulse switching applications where low saturation voltage and stable gain across temperature are critical. Its 60 V V_CEO rating supports use in 48 V rail systems, while its 175 MHz f_T enables reliable operation up to high-frequency switching edges (e.g., <100 ns turn-on/turn-off).

Thermal design relies on its defined R_th(j-amb) = 175 °C/W (free air) and R_th(j-case) = 70 °C/W, with derating starting above 25°C. The device is characterized at T_amb = 25°C, with validated safe operating area (SOA) curves covering single-pulse and DC conditions up to 2 A.

Key Specifications

Pinout & Package

Package: TO-92-compatible E-Line (3-lead plastic case), lead-form compatible with standard TO-92 footprint and automated insertion equipment.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MJD122G and BCX56-16, the ZTX651STOB uniquely balances 2 A capability, 60 V rating, low 0.12 V V_CE(sat), and TO-92 compatibility-making it optimal for space-constrained, thermally moderate 48 V industrial switching where discrete BJT simplicity is preferred over MOSFET gate-drive complexity.

Availability

ZTX651STOB is available at Aetrix Electronics and suitable for industrial power supply control, DC motor speed regulation, relay driver circuits, and LED current regulation requiring stable component supply and long-term manufacturability.

Supply support for ZTX651STOB 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, computing, and consumer markets.

The ZTX651STOB belongs to Diodes' legacy ZTX series of medium-power BJTs, designed specifically for robust, cost-effective switching and amplification in space- and thermal-constrained industrial control modules.

FAQ

What is the maximum continuous collector current for ZTX651STOB?

The ZTX651STOB is rated for 2 A continuous collector current (I_C) at T_amb = 25°C with appropriate PCB copper area. Derating applies above 25°C per the 5.7 mW/°C slope shown in the thermal characteristics curve. At 70°C ambient, maximum continuous I_C drops to approximately 1.3 A to maintain junction temperature ≤ 150°C.

Can ZTX651STOB replace ZTX650 in existing designs?

Yes, the ZTX651STOB is a direct upgrade to the ZTX650 with identical pinout and package, but offers higher V_CEO (60 V vs. 45 V) and V_CBO (80 V vs. 60 V), plus identical V_CE(sat) and f_T. No layout or bias changes are required, and the improved voltage margin enhances reliability in 48 V systems subject to line transients.

What is the recommended base drive for saturation switching?

For guaranteed saturation at I_C = 2 A, apply I_B ≥ 200 mA (i.e., I_C/I_B ≤ 10), resulting in V_CE(sat) ≤ 0.3 V. A 10 Ω series base resistor is typical when driven from a 3.3 V or 5 V logic source; ensure the driver can source ≥200 mA peak without voltage droop.

Is ZTX651STOB suitable for linear amplifier applications?

Yes-the ZTX651STOB exhibits stable h_FE (typically 100–300 at I_C = 100 mA) and low distortion in Class-A configurations. However, its 1 W P_tot limits output power to ~300 mW in unheatsinked linear use; for higher power, consider TO-220 alternatives with lower R_th(j-amb).