onsemi 1N976B_T50A

Overview

1N976B_T50A from Fairchild Semiconductor is a 39 V, ±5% tolerance, 500 mW glass-passivated Zener diode in DO-35 package, designed for precision voltage regulation and reference applications in power supply feedback loops, overvoltage protection circuits, and analog signal conditioning stages.

For engineers reviewing the 1N976B_T50A datasheet, pinout, applications, or equivalent options, key selection considerations include its nominal zener voltage of 39 V at 5 mA, dynamic impedance of 8.5 Ω, maximum zener current of 80 mA, and operation across –65°C to +200°C.

Technical Context

The 1N976B_T50A operates as a two-terminal voltage reference device with sharp reverse-breakdown characteristics. Its zener voltage is specified at I_Z = 5 mA, with typical dynamic impedance (Z_Z) of 8.5 Ω measured at 0.1×I_Z (0.5 mA AC) and 60 Hz.

It features glass-passivated junction construction in a DO-35 axial leaded package, enabling stable long-term voltage reference performance under thermal cycling and humidity stress. The cathode is marked by a color band on the glass case.

Key Specifications

Pinout & Package

DO-35 glass axial package with cathode indicated by a single color band. Leads are tinned copper-clad steel, 0.46 mm diameter, 25.4 mm minimum length. No internal bonding wires; hermetically sealed glass body provides moisture resistance and long-term parameter stability.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 1N4739A and BZX55-C39, the 1N976B_T50A offers superior low-current regulation stability and explicit lead-temperature derating guidance, making it preferred for precision analog references and thermally dense industrial modules.

Availability

1N976B_T50A is available at Aetrix Electronics and suitable for switch-mode power supplies, industrial sensor interfaces, overvoltage protection circuits, and programmable current sources requiring stable component supply and long-lifecycle support.

Supply support for 1N976B_T50A 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

Fairchild Semiconductor was a U.S.-based semiconductor company specializing in power management, analog, and discrete devices, acquired by ON Semiconductor in 2016.

The 1N957B–1N979B series was developed for high-reliability voltage reference applications in automotive, industrial, and telecom infrastructure where long-term parametric stability and wide temperature operation are critical.

FAQ

What is the nominal zener voltage of the 1N976B_T50A and at what test current is it specified?

The 1N976B_T50A has a nominal zener voltage of 39 V, specified at a test current of 5 mA. Its minimum and maximum values are 39.0 V and 40.95 V respectively, measured at thermal equilibrium with lead temperature at 30°C ± 1°C and 3/8" lead length. This defines the core regulation point used in all downstream design calculations for the 1N976B_T50A.

Does the 1N976B_T50A have a defined power derating curve, and if so, how is it applied?

Yes, the 1N976B_T50A has a defined power derating curve: full 500 mW dissipation is rated only when lead temperature (T_L) is ≤ 75°C. Above that, power must be reduced at 4.0 mW/°C. This linear derating allows engineers to calculate safe operating current for elevated ambient or board temperatures - for example, at T_L = 100°C, max power drops to 400 mW, limiting I_Z to ~10.3 mA at 39 V for the 1N976B_T50A.

What is the zener impedance (Z_Z) of the 1N976B_T50A, and why does it matter in circuit design?

The 1N976B_T50A has a typical zener impedance of 8.5 Ω at I_Z = 5 mA. This value directly impacts regulation accuracy: for every 1 mA change in load current, output voltage shifts by ~8.5 mV. Low Z_Z enables tighter voltage control in feedback loops and better ripple rejection - critical when using the 1N976B_T50A in precision references or low-noise analog stages.

How is the cathode identified on the 1N976B_T50A DO-35 package?

The cathode of the 1N976B_T50A is identified by a single color band on the glass body of the DO-35 package. This band marks the cathode end, consistent with industry-standard polarity marking for axial-leaded Zener diodes. When installed, the banded end connects to the higher-potential node (e.g., input rail), while the unbanded anode connects to ground or return - essential for correct 1N976B_T50A operation in shunt regulation.

What is the maximum reverse leakage current (I_R) specification for the 1N976B_T50A, and under what condition is it measured?

The maximum reverse leakage current for the 1N976B_T50A is 0.25 μA, measured at a reverse voltage (V_R) of 31.5 V - which is 80% of its minimum rated zener voltage. This ultra-low leakage ensures minimal parasitic current draw in high-impedance bias networks, such as those found in battery-powered sensor nodes or precision op-amp references where the 1N976B_T50A serves as a stable voltage anchor.