Microchip Technology 1N981B

Overview

1N981B from Microsemi is a silicon 500 mW axial-leaded Zener diode in DO-35 (DO-204AH) package, rated for 68 V nominal Zener voltage with ±5% tolerance, 1.8 mA Zener test current, and +0.097 %/°C temperature coefficient. It regulates voltage across wide operating current and temperature ranges (-65°C to +175°C), and is used in precision reference and overvoltage protection circuits.

For engineers reviewing the 1N981B datasheet, 1N981B pinout, 1N981B application, or 1N981B equivalent, key selection criteria include its 68 V regulation point, low 1.8 mA test current requirement, tight thermal stability (+0.097 %/°C), RoHS-compliant e3 variant availability, and compatibility with standard axial-lead PCB mounting.

Technical Context

The 1N981B operates as a reverse-biased voltage reference device, maintaining stable 68 V output across varying load currents from 0.25 mA (IZK) up to 5.5 mA (IZM) at 75°C lead temperature. Its Zener impedance is 2000 Ω at IZT, and it exhibits minimal capacitance per Figure 3 of the datasheet.

It features a hermetically sealed glass DO-35 package with tin-lead or matte-tin plating, cathode band marking, and is rated for 0.5 W steady-state power at TL < 50°C (3/8" from body). Forward voltage is ≤1.3 V at 200 mA, and ESD immunity meets MIL-STD-750 Method 1020.

Key Specifications

Pinout & Package

Package: DO-35 (DO-204AH), hermetically sealed axial-leaded glass body, 0.2 g weight, cathode indicated by colored band.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 1N981B, the 1N4744A serves different voltage classes and cannot replace it in 68 V roles, while BZX55C68 offers same nominal voltage but differs in test current and thermal coefficient-requiring verification of regulation stability under actual operating conditions.

Availability

1N981B is available at Aetrix Electronics and suitable for voltage reference circuits, overvoltage clamp designs, and power supply feedback networks requiring stable component supply and long-lifecycle support.

Supply support for 1N981B 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

Microsemi (now part of Microchip Technology) is a U.S.-based semiconductor company specializing in high-reliability, radiation-hardened, and precision analog components for aerospace, defense, and industrial markets.

The 1N957B–1N992B series was designed specifically for demanding applications requiring stable Zener regulation across extreme temperatures and long operational lifetimes, with emphasis on hermetic packaging and JEDEC compliance.

FAQ

What is the nominal Zener voltage and tolerance of the 1N981B?

The 1N981B has a nominal Zener voltage of 68 V with a tolerance of ±5%, as indicated by the "B" suffix per JEDEC standard. This means the actual regulation voltage falls between 64.6 V and 71.4 V at 1.8 mA test current and 25°C ambient. The 1N981B maintains this specification across its full operating temperature range of −65°C to +175°C.

What is the maximum continuous Zener current for the 1N981B?

The maximum DC Zener current (IZM) for the 1N981B is 5.5 mA when measured at a 75°C lead temperature located 3/8 inch from the body. This value corresponds to a power dissipation limit of 400 mW under those thermal conditions. At lower lead temperatures, the device can sustain higher current briefly, but steady-state design must respect the 5.5 mA limit to avoid junction overheating. The 1N981B must be mounted with appropriate copper pad area and trace width to maintain thermal performance.

Is the 1N981B RoHS compliant?

Yes, the RoHS-compliant version of the 1N981B is designated as 1N981B-e3, where the "e3" suffix indicates annealed matte-tin plating per JEDEC standards. The base 1N981B uses traditional tin-lead plating. Both variants share identical electrical specifications, including 68 V nominal Zener voltage, 1.8 mA test current, and +0.097 %/°C temperature coefficient. The 1N981B-e3 is fully compatible with lead-free soldering processes up to 260°C for 10 seconds.

What package type does the 1N981B use, and how is polarity marked?

The 1N981B uses the DO-35 (also known as DO-204AH) axial-leaded glass package. Polarity is marked by a visible cathode band near one end of the glass body; the banded end is the cathode and must be connected to the more positive potential during Zener operation. The anode is the non-banded lead. This marking aligns with JEDEC standard orientation and ensures correct installation in voltage regulation or clamping circuits using the 1N981B.

How does the temperature coefficient of the 1N981B affect its regulation accuracy?

The 1N981B has a temperature coefficient of +0.097 %/°C, meaning its Zener voltage increases by approximately 66 mV per °C rise in junction temperature. Over a 100°C span (e.g., −25°C to +75°C), this results in ~6.6 V total drift. Designers using the 1N981B in precision references must account for this slope via compensation networks or operating-point selection. The 1N981B's coefficient is typical for mid-voltage Zeners and is documented in Figure 2 of the Microsemi datasheet.