Microchip Technology 1N971A

Overview

1N971A from Microsemi is a silicon 500 mW axial-lead Zener diode with nominal Zener voltage 27 V, ±10% tolerance (A suffix), 41 mA maximum DC Zener current (IZM), and 750 Ω maximum Zener impedance at 4.6 mA test current. It operates across –65°C to +175°C and is used for precision voltage reference and overvoltage protection in industrial power supplies.

For engineers reviewing the 1N971A datasheet, 1N971A pinout, 1N971A application, or 1N971A equivalent, key selection criteria include its 27 V regulation point, DO-35 glass package thermal resistance (310°C/W on FR4), low reverse leakage (≤5 μA at 20.6 V), and JEDEC-registered construction for legacy design continuity.

Technical Context

The 1N971A functions as a two-terminal voltage reference device operating in reverse breakdown mode. Its Zener voltage is specified at 4.6 mA test current (IZT), with dynamic impedance measured at 10% AC superimposed on IZT per JEDEC standard.

It exhibits a positive temperature coefficient of +0.090 %/°C and maintains regulation stability across wide current (0.25–41 mA) and temperature (–65°C to +175°C) ranges. The DO-35 glass package provides hermetic sealing and ESD insensitivity per MIL-STD-750 Method 1020.

Key Specifications

Pinout & Package

Package: DO-35 (DO-204AH), hermetically sealed axial-lead glass case with cathode band marking. Tin-lead or RoHS-compliant matte-tin plating, weight 0.2 g.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 1N971A, the 1N971B offers improved voltage accuracy without layout change, while the MMBZ5256B enables miniaturization at the cost of reduced power handling and altered thermal management requirements.

Availability

1N971A is available at Aetrix Electronics and suitable for industrial power supplies, overvoltage protection circuits, legacy equipment repair, and aerospace sensor biasing requiring stable component supply and long-term obsolescence mitigation.

Supply support for 1N971A 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 high-voltage analog components.

The 1N971A belongs to Microsemi's legacy JEDEC-registered 1N957B–1N992B Zener series, designed for ruggedized voltage regulation in aerospace, defense, and industrial systems where long-term reliability and specification consistency are critical.

FAQ

What is the Zener voltage tolerance of the 1N971A?

The 1N971A has a nominal Zener voltage of 27 V with ±10% tolerance, indicated by the "A" suffix per JEDEC standard. This means the actual measured VZ at 4.6 mA test current falls between 24.3 V and 29.7 V at 25°C. The tolerance reflects cost-optimized performance for non-critical regulation tasks where tighter accuracy is unnecessary.

Can the 1N971A be used in place of the 1N971B?

Yes, the 1N971A can substitute for the 1N971B in most applications, but with reduced voltage accuracy: 1N971A is ±10% while 1N971B is ±5%. Both share identical DO-35 packaging, thermal ratings, and electrical curves. Use 1N971A only where system-level voltage margin accommodates the wider tolerance band.

What is the maximum power dissipation for the 1N971A on a standard FR4 PCB?

The 1N971A delivers 480 mW maximum power dissipation when mounted on an FR4 PCB with 1 oz copper, 4 mm² pads, and 1 mm × 25 mm traces, per Microsemi's thermal characterization. At lead temperature <50°C (3/8″ from body), it supports full 500 mW-derating begins above 50°C per the published power curve in Figure 1.

Does the 1N971A require external ESD protection?

No, the 1N971A is nonsensitive to ESD per MIL-STD-750 Method 1020 and does not require external protection circuitry during handling or operation. Its glass DO-35 construction and metallurgical design inherently suppress electrostatic discharge effects, making it suitable for manual assembly in uncontrolled environments.

What is the temperature coefficient of the 1N971A, and how does it affect regulation?

The 1N971A has a temperature coefficient of +0.090 %/°C, meaning its Zener voltage increases by approximately 24.3 mV per °C rise above 25°C. This positive drift must be accounted for in high-precision references; however, it improves stability in circuits where ambient temperature rises concurrently with load-induced heating.