onsemi 1N5257BTR

Overview

1N5257BTR from Fairchild Semiconductor is a 33 V ±5% Zener diode in DO-35 glass package, rated for 500 mW power dissipation, with 58 Ω dynamic impedance at 14 mA test current and 0.25 μA reverse leakage at 25.2 V. It provides precision voltage regulation in low-power analog reference and overvoltage protection circuits.

For engineers reviewing the 1N5257BTR datasheet, pinout, applications, or equivalent options, this device serves as a stable, low-current voltage clamp in power supply feedback paths, sensor biasing networks, and IC voltage monitoring circuits where thermal stability and tight tolerance are critical.

Technical Context

The 1N5257BTR operates as a two-terminal silicon Zener diode optimized for breakdown regulation in the 33 V range. Its junction temperature range spans –65°C to +200°C, and it features a negative temperature coefficient of +0.092 %/°C - typical for mid-voltage Zeners - enabling predictable drift behavior in ambient-temperature-varying designs.

Designed for DC or low-frequency regulation, it exhibits 14 mA nominal Zener test current (IZ), 25.2 V maximum VR for IR = 0.25 μA, and forward voltage ≤1.2 V at 200 mA - confirming standard PN-junction conduction characteristics on the anode-cathode path outside breakdown.

Key Specifications

Pinout & Package

DO-35 glass axial package: hermetically sealed, 2.0 mm diameter × 4.56 mm length body, cathode indicated by single color band; leads are tinned copper, 0.533 mm diameter, 3.05 mm lead length minimum.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 1N4749A and BZX55-C33, the 1N5257BTR delivers optimal balance of DO-35 footprint, 58 Ω impedance at 14 mA, and +0.092 %/°C TC - making it preferred for compact, medium-precision analog references where thermal and layout constraints exclude larger packages or higher-leakage alternatives.

Availability

1N5257BTR is available at Aetrix Electronics and suitable for industrial sensor biasing, microcontroller reset circuits, linear power supply references, and overvoltage protection clamps requiring stable component supply and consistent parametric performance across production lots.

Supply support for 1N5257BTR 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, signal conditioning, and discrete components before its acquisition by ON Semiconductor in 2016; its legacy Zener diodes remain widely deployed in industrial and commercial designs.

The 1N52xxB series was engineered for general-purpose voltage regulation in cost-sensitive, space-constrained applications - emphasizing tight tolerance, stable TC, and robust glass-package reliability across extended temperature ranges.

FAQ

What is the Zener voltage tolerance of the 1N5257BTR?

The 1N5257BTR has a Zener voltage tolerance of ±5% around its nominal 33 V rating, meaning the actual measured VZ falls between 31.35 V and 34.65 V when tested at 14 mA. This tolerance is guaranteed per the Fairchild 1N5221B–1N5263B datasheet Rev. 4.10 and applies to all units shipped as 1N5257BTR under standard qualification screening.

Can the 1N5257BTR be used in surface-mount designs?

No - the 1N5257BTR uses a DO-35 glass axial package with radial leads, designed exclusively for through-hole mounting. It lacks SMT-compatible terminations or tape-and-reel packaging. For surface-mount equivalents, consider SOD-123 or SOD-323 packaged Zeners like MMBZ5257BS, which offer comparable 33 V regulation but require board redesign.

What is the maximum reverse leakage current for the 1N5257BTR?

The maximum reverse leakage current (IR) for the 1N5257BTR is 0.25 μA, specified at VR = 25.2 V (76% of nominal VZ). This value is confirmed in the Electrical Characteristics table of the Fairchild 1N5221B–1N5263B datasheet and reflects worst-case leakage under defined test conditions - critical for high-impedance bias networks.

Does the 1N5257BTR have a positive or negative temperature coefficient?

The 1N5257BTR has a positive temperature coefficient of +0.092 %/°C, meaning its Zener voltage increases slightly with rising junction temperature. This value is documented in the datasheet's Electrical Characteristics table and is typical for Zeners in the 30–40 V range, enabling predictable drift compensation in temperature-critical references.

Is the 1N5257BTR suitable for automotive applications?

No - the 1N5257BTR is a commercial-grade device not qualified for automotive use. Fairchild's Authorized Use policy explicitly excludes applications requiring extraordinary reliability, including automotive or safety-critical systems, unless approved in writing. For AEC-Q200-compliant alternatives, consult ON Semiconductor's NZ9F33V or similar qualified Zener families.