Microchip Technology 1N974B

Overview

1N974B from Microsemi is a silicon 500 mW axial-leaded Zener diode in DO-35 (DO-204AH) package, rated for 36 V nominal Zener voltage with ±5% tolerance, 3.4 mA Zener test current, 1000 Ω dynamic impedance at I_ZT, and maximum 10 mA DC Zener current. It operates across –65°C to +175°C and serves as a precision voltage reference or shunt regulator in low-power analog circuits.

For engineers reviewing the 1N974B datasheet, 1N974B pinout, 1N974B application, or 1N974B equivalent, key selection criteria include its 36 V regulation point, tight thermal coefficient (+0.093 %/°C), glass-body DO-35 mechanical robustness, RoHS-compliant e3 variant availability, and compatibility with through-hole PCB mounting under industrial temperature stress.

Technical Context

The 1N974B functions as a shunt-connected voltage regulator, maintaining stable 36 V output by conducting reverse current above its breakdown threshold. Its Zener impedance of 1000 Ω at 3.4 mA ensures predictable regulation slope, while its 0.5 W power rating is derated linearly above 50°C lead temperature.

Designed for operation with cathode band positive relative to anode, it exhibits minimal capacitance (typical <2 pF per Figure 3), low ESD sensitivity (MIL-STD-750 Method 1020), and inherent radiation hardness per MicroNote 050 - making it suitable for aerospace-adjacent and high-reliability analog signal conditioning.

Key Specifications

Pinout & Package

Package: DO-35 (DO-204AH), hermetically sealed axial-leaded glass body, 0.2 g weight, tin-lead or RoHS-compliant matte-tin plating, 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 1N974B, the 1N4738A offers higher power and lower impedance but shifts regulation to 33 V, requiring redesign of feedback or clamp thresholds; the BZX55-C36 matches 36 V and package but delivers superior impedance performance at slightly higher test current, making it suitable for noise-sensitive references where lead inductance must be minimized.

Availability

1N974B is available at Aetrix Electronics and suitable for overvoltage protection, fixed voltage reference, and power supply feedback applications requiring stable component supply across extended temperature ranges and long product lifecycles.

Supply support for 1N974B 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 for aerospace, defense, and industrial markets.

The 1N957B–1N992B series was engineered to deliver JEDEC-standardized, glass-encapsulated Zener regulation with extended temperature resilience and proven field reliability - targeting mission-critical analog subsystems where long-term parametric stability is non-negotiable.

FAQ

What is the nominal Zener voltage and tolerance of the 1N974B?

The 1N974B has a nominal Zener voltage of 36 V with a ±5% tolerance, as defined by the "B" suffix per JEDEC registration. This means the actual measured V_Z falls between 34.2 V and 37.8 V at 3.4 mA test current and 25°C. The 1N974B achieves this specification under standardized test conditions described in Note 2 of the Microsemi datasheet, including 20-second stabilization and controlled lead temperature.

What is the maximum continuous Zener current for the 1N974B?

The maximum DC Zener current (I_ZM) for the 1N974B is 10 mA, calculated to maintain power dissipation at or below 400 mW at a 75°C lead temperature. At room temperature (25°C), the device can sustain up to 13.9 mA before reaching its 500 mW rating - but design margins should respect the 10 mA I_ZM limit to ensure reliability across temperature extremes. This value is explicitly listed in the Electrical Characteristics table on page 2 of the 1N974B datasheet.

Does the 1N974B have RoHS-compliant variants?

Yes, the 1N974B is available in RoHS-compliant form with the "e3" suffix (e.g., 1N974Be3), featuring annealed matte-tin plating instead of traditional tin-lead. This variant meets EU RoHS Directive 2011/65/EU and is solderable per MIL-STD-750 Method 2026. The electrical and thermal specifications remain identical to the standard 1N974B; only the termination plating differs. Both versions share the same DO-35 package and marking convention.

What is the Zener impedance of the 1N974B and why does it matter?

The 1N974B has a maximum Zener impedance (Z_ZT) of 1000 Ω measured at its 3.4 mA test current. This parameter quantifies how much the output voltage changes with varying current - a lower Z_ZT indicates stiffer regulation. At 1000 Ω, a ±1 mA change in Zener current causes approximately ±1 V shift in regulated voltage, which must be accounted for in low-current reference designs. The 1N974B's Z_ZT is consistent with its 36 V rating and 500 mW class.

Can the 1N974B be used in high-temperature environments like automotive under-hood applications?

Yes, the 1N974B is rated for continuous operation from –65°C to +175°C junction temperature, with thermal resistance of 250°C/W junction-to-lead (at 3/8″ lead length). This makes it suitable for under-hood automotive use when mounted with adequate copper pour and lead length control. Its radiation hardness (per MicroNote 050) and low ESD sensitivity further support deployment in harsh environments where the 1N974B maintains regulation integrity without derating below 175°C.