onsemi 1N976B_T50R

Overview

1N976B_T50R from Fairchild Semiconductor is a 39 V, ±5% tolerance, 500 mW glass-encapsulated 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_T50R datasheet, pinout, applications, or equivalent options, key selection criteria include zener voltage tolerance (±5%), dynamic impedance (10 Ω @ 33 mA), leakage current (0.25 μA @ 31.5 V), and thermal derating (4.0 mW/°C above 75°C).

Technical Context

The 1N976B_T50R operates as a two-terminal voltage reference device with sharp reverse breakdown at nominal 39 V. Its DO-35 glass package ensures hermetic sealing and stable long-term V_Z drift under industrial temperature cycling (-65°C to +200°C).

It delivers regulated output with low dynamic impedance (10 Ω) at I_Z = 33 mA and maintains sub-microampere leakage (IR ≤ 0.25 μA) at VR = 31.5 V, enabling high-accuracy biasing in low-power analog circuits without significant quiescent current penalty.

Key Specifications

Pinout & Package

DO-35 glass axial package with cathode indicated by color band; two-terminal device requiring no external biasing or control signals.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 1N976B_T50R, 1N4739A offers higher power handling at the cost of larger size, while BZX55-C39 provides marginally better temperature coefficient but identical package and power rating-making it a drop-in alternative only if tighter tempco is required.

Availability

1N976B_T50R is available at Aetrix Electronics and suitable for power supply feedback, overvoltage protection, and analog reference applications requiring stable component supply across industrial, automotive, and instrumentation programs.

Supply support for 1N976B_T50R 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 components before its acquisition by ON Semiconductor in 2016.

The 1N957B–1N979B series was developed as a standard family of general-purpose Zener diodes targeting cost-sensitive, high-reliability voltage reference needs in legacy industrial and consumer power systems.

FAQ

What is the nominal zener voltage and tolerance of the 1N976B_T50R?

The 1N976B_T50R has a nominal zener voltage of 39 V with a tolerance of ±5%, measured at I_Z = 33 mA and T_L = 30°C ± 1°C. This tolerance ensures consistent regulation performance across manufacturing batches and supports use in applications where tight voltage referencing is needed without active trimming. The 1N976B_T50R maintains this specification under defined thermal and current conditions per Fairchild's Rev. F1 datasheet.

What is the maximum power dissipation and thermal derating behavior of the 1N976B_T50R?

The 1N976B_T50R is rated for 500 mW power dissipation at lead temperature (T_L) ≤ 75°C with 3/8″ lead length. Above 75°C, it derates linearly at 4.0 mW/°C. This derating curve must be applied in thermal design to avoid junction overheating. The 1N976B_T50R's DO-35 package relies on lead conduction for heat transfer, so PCB layout and ambient airflow directly impact real-world power handling capability.

What is the zener impedance of the 1N976B_T50R and why does it matter?

The 1N976B_T50R exhibits a zener impedance (Z_Z) of 10 Ω at I_Z = 33 mA. This low dynamic impedance means the device maintains stable output voltage despite variations in load current-critical for feedback loop stability in switching regulators. A lower Z_Z reduces output ripple and improves regulation accuracy, making the 1N976B_T50R suitable for precision analog reference roles where voltage deviation must stay within tight bounds.

How is the cathode identified on the 1N976B_T50R package?

The cathode of the 1N976B_T50R is marked by a distinct color band on the DO-35 glass body, consistent with industry-standard polarity marking for axial-leaded Zener diodes. This band must be oriented toward the higher-potential node in shunt regulator configurations. The 1N976B_T50R follows Fairchild's top-marking convention: first line is the F logo, second line reads "76", third line reads "B"-confirming part identity and revision. Correct orientation is essential to ensure proper reverse-bias operation.

What are the operating and storage temperature limits for the 1N976B_T50R?

The 1N976B_T50R is specified for operation and storage from -65°C to +200°C, reflecting its hermetically sealed DO-35 glass construction. This wide range supports deployment in extreme environments such as automotive under-hood modules, oilfield instrumentation, and aerospace subsystems. The 1N976B_T50R retains electrical specifications across this range, though V_Z exhibits a known positive temperature coefficient (~0.07%/°C), which must be accounted for in high-precision designs.