onsemi 1N4749A_NT50A

Overview

1N4749A_NT50A from ON Semiconductor is a 24 V, 1 W Zener diode in DO-41 glass package, rated for ±5% tolerance, 10.5 Ω dynamic impedance at 15 mA test current, and operating from –65 °C to +200 °C - used for precision voltage regulation in power supply feedback loops and overvoltage protection circuits.

For engineers reviewing the 1N4749A_NT50A datasheet, pinout, applications, or equivalent options, key selection criteria include Zener voltage accuracy, thermal derating (6.67 mW/°C above 50 °C), peak reverse surge capability (190 mA non-repetitive), leakage current ≤5 µA at 18.2 V, and DO-41 mechanical compatibility with through-hole PCB layouts.

Technical Context

The 1N4749A_NT50A operates as a two-terminal voltage reference device, maintaining stable reverse breakdown at nominal 24 V under controlled test current (IZ = 15 mA). Its Zener impedance (ZZ = 10.5 Ω) and knee impedance (ZZK = 25 Ω at IZK = 0.25 mA) define regulation stiffness across load and line variations.

Designed for DC voltage clamping and shunt regulation, it relies on thermal equilibrium at TL = 30 °C (3/8″ lead length) for VZ specification compliance. The DO-41 package enables axial lead mounting with cathode band identification and supports 1.0 W power dissipation up to 50 °C ambient before linear derating begins.

Key Specifications

Pinout & Package

DO-41 glass axial package with cathode identified by a single color band. Leads are tinned copper-clad steel; body diameter 2.0–2.7 mm, length 4.5–6.0 mm, lead diameter 0.4–0.6 mm.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar Zener voltage regulation applications.

Compared with 1N4749A_NT50A, the bare 1N4749A offers identical electrical behavior with different packaging logistics, while BZX55-C24 trades 50% lower power rating and reduced surge capacity for smaller size - making 1N4749A_NT50A optimal for high-reliability 24 V shunt regulation where thermal margin and transient immunity are critical.

Availability

1N4749A_NT50A is available at Aetrix Electronics and suitable for industrial power supplies, PLC input modules, and automotive sensor interfaces requiring stable component supply and long-term manufacturability.

Supply support for 1N4749A_NT50A 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

ON Semiconductor is a global semiconductor manufacturer specializing in energy-efficient power management, analog, sensing, and connectivity solutions for automotive, industrial, and cloud infrastructure markets.

The 1N47xxA series was developed for general-purpose Zener regulation in cost-sensitive, high-volume applications - emphasizing tight voltage tolerance, repeatable breakdown characteristics, and rugged DO-41 packaging for through-hole reliability.

FAQ

What is the Zener voltage tolerance of the 1N4749A_NT50A?

The 1N4749A_NT50A has a Zener voltage tolerance of ±5%, with a specified range of 22 V (minimum) to 25.2 V (maximum) at 15 mA test current. This tolerance is guaranteed across the full operating temperature range and reflects manufacturing consistency for reliable voltage reference design. The 1N4749A_NT50A maintains this spec without external calibration or trimming.

Can the 1N4749A_NT50A replace the 1N4748A in a 22 V regulator circuit?

No - the 1N4749A_NT50A is rated for 24 V nominal Zener voltage (22–25.2 V range), whereas the 1N4748A is rated for 22 V (20.9–23.1 V). Substituting the 1N4749A_NT50A would raise regulated output by ~2 V, potentially exceeding downstream component ratings. Always verify V_Z match before interchanging 1N47xxA devices.

What is the maximum allowable ambient temperature for continuous 1.0 W operation of the 1N4749A_NT50A?

The 1N4749A_NT50A supports full 1.0 W power dissipation only when lead temperature (T_L) is maintained at ≤50 °C, typically corresponding to an ambient temperature of ~35–40 °C depending on PCB copper area and airflow. Above 50 °C lead temperature, power must be linearly derated at 6.67 mW/°C - so at 75 °C T_L, max power drops to 833 mW. The 1N4749A_NT50A datasheet defines thermal limits strictly at the leads, not case or ambient.

Does the 1N4749A_NT50A have a specified Zener impedance at low current?

Yes - the 1N4749A_NT50A specifies knee impedance (Z_ZK) of 25 Ω at I_ZK = 0.25 mA, which characterizes its regulation behavior near the onset of breakdown. This value is critical for low-current bias networks and precision reference dividers where operation below 15 mA is required. The 1N4749A_NT50A's 25 Ω Z_ZK ensures usable regulation even at microampere-level currents.

Is the 1N4749A_NT50A suitable for automotive under-hood applications?

Yes - the 1N4749A_NT50A is qualified for operation from –65 °C to +200 °C junction temperature, covering under-hood environments where ambient temperatures exceed 125 °C. Its DO-41 glass package provides hermetic reliability, and the 1N4749A_NT50A's 190 mA non-repetitive surge rating supports ISO 7637-2 pulse testing. Thermal design must ensure T_J stays within limits under worst-case power dissipation.