onsemi 1N959B_T50A

Overview

1N959B_T50A from Fairchild Semiconductor is a 5% tolerance, 7.79 V nominal Zener diode in DO-35 glass package, rated for 500 mW power dissipation at TL ≤ 75°C with 4.0 mW/°C derating, and operates from –65°C to +200°C. It delivers stable voltage reference in low-power analog circuits, precision biasing networks, and overvoltage protection clamps.

For engineers reviewing the 1N959B_T50A datasheet, pinout, applications, or equivalent options, key selection criteria include zener voltage (7.79 V typ), zener impedance (15 Ω @ 6.5 mA), leakage current (0.5 μA @ 6.2 V), maximum zener current (50 mA), and DO-35 thermal and mechanical constraints.

Technical Context

The 1N959B_T50A functions as a silicon planar passivated Zener diode optimized for stable reverse-breakdown regulation under DC or low-frequency conditions. Its 7.79 V nominal zener voltage is specified at 6.5 mA test current, with typical zener impedance of 15 Ω and knee impedance of 700 Ω at 0.25 mA.

Designed for leaded through-hole mounting, it uses a DO-35 axial glass package with cathode band marking and supports operation across –65°C to +200°C junction temperature range. Power dissipation is thermally limited to 500 mW at lead temperature ≤ 75°C, derating linearly at 4.0 mW/°C above that point.

Key Specifications

Pinout & Package

DO-35 glass axial package with cathode indicated by color band on body; two-terminal device with no internal polarity reversal or auxiliary pins.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 1N959B_T50A, the 1N4734A offers higher power but mismatched voltage and package, while the BZX55C7V5 matches DO-35 form factor and tolerance but shifts regulation by 0.29 V-requiring recalibration of associated resistor dividers or feedback networks.

Availability

1N959B_T50A is available at Aetrix Electronics and suitable for automotive sensor biasing, industrial analog reference design, and overvoltage clamp protection requiring stable component supply and long-lifecycle support.

Supply support for 1N959B_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 before its acquisition by ON Semiconductor in 2016.

The 1N957B–1N979B series was designed as a general-purpose, high-reliability Zener diode family for voltage regulation and protection in cost-sensitive industrial and automotive systems.

FAQ

What is the nominal zener voltage of the 1N959B_T50A?

The 1N959B_T50A has a nominal zener voltage of 7.79 V, measured at a test current of 6.5 mA and lead temperature of 30°C ± 1°C. This value falls within a guaranteed range of 7.14 V (min) to 8.61 V (max) due to its 5% tolerance. The 1N959B_T50A maintains this regulation characteristic across its full operating temperature range and is specified with typical zener impedance of 15 Ω at the same test condition.

Does the 1N959B_T50A have a cathode marking, and how is it identified?

Yes, the 1N959B_T50A features a visible cathode band on the DO-35 glass body, consistent with industry-standard polarity marking. The cathode is the end marked with a distinct color band, and the anode is the unmarked end. This marking aligns with Fairchild's top-marking specification: Line 1 shows the Fairchild "F" logo, Line 2 displays "59", and Line 3 shows "B", confirming the 1N959B_T50A identity and polarity orientation for manual or automated assembly verification.

What is the maximum power dissipation rating for the 1N959B_T50A?

The 1N959B_T50A is rated for 500 mW power dissipation at a lead temperature (T_L) of ≤ 75°C with 3/8″ lead length. Above 75°C, it derates linearly at 4.0 mW/°C. This rating reflects real-world thermal performance under standard mounting conditions-not a theoretical junction limit-and must be applied with appropriate PCB copper pour and lead length to avoid exceeding the 200°C maximum junction temperature. The 1N959B_T50A's DO-35 package relies on lead conduction for heat transfer, making thermal layout critical.

How does the 1N959B_T50A perform at elevated temperatures?

The 1N959B_T50A is characterized for continuous operation from –65°C to +200°C junction temperature, with electrical parameters guaranteed at 25°C and derated per published curves. Its zener voltage exhibits a positive temperature coefficient near 7.5 V, resulting in moderate V_Z drift (~+0.05%/°C) above 25°C. The 1N959B_T50A maintains functional regulation integrity across this full range, validated in automotive under-hood environments where sustained 150°C ambient is common, provided power dissipation remains within thermal limits.

Is the 1N959B_T50A suitable for precision voltage reference applications?

The 1N959B_T50A provides mid-precision regulation with 5% initial tolerance and typical zener impedance of 15 Ω, making it suitable for applications where ±1% output stability is acceptable-such as sensor biasing or reset threshold generation-but not for high-accuracy references requiring <0.1% tolerance or <5 ppm/°C tempco. For such cases, dedicated reference ICs like the REF50xx series are recommended. The 1N959B_T50A excels in cost-sensitive, robust, and thermally demanding roles where its DO-35 reliability and wide temperature range outweigh ultra-tight spec needs.