Diodes Incorporated 1N4737A-T

Overview

1N4737A-T from Diodes Incorporated is a 1.0 W, 7.5 V ±5% Zener diode in DO-41 glass package, designed for precision voltage regulation and reference applications in power supply feedback loops, overvoltage protection circuits, and analog signal conditioning stages. It delivers 34 mA test current, 4.0 Ω dynamic impedance at I_ZT, <5 µA reverse leakage at 5.0 V, and exhibits +0.02 to +0.065 %/°C temperature coefficient.

For engineers reviewing the 1N4737A-T datasheet, 1N4737A-T pinout, 1N4737A-T application, or 1N4737A-T equivalent, key selection criteria include Zener voltage tolerance, thermal resistance (175 °C/W), surge current rating (605 mA @ 8.3 ms), cathode-band polarity marking, and DO-41 lead-form compatibility with through-hole PCB assembly.

Technical Context

This discrete Zener diode operates in reverse breakdown mode to maintain stable DC reference voltage under varying load and temperature conditions. Its 7.5 V nominal Zener voltage is specified at 34 mA test current (I_ZT) with 4.0 Ω impedance at that point and 700 Ω at knee current (I_ZK = 0.5 mA).

The device features a glass-passivated DO-41 package with Sn96.5Ag3.5 terminations, UL 94V-0 flammability rating, and operates across –65 °C to +175 °C. Thermal derating begins above 50 °C at 6.67 mW/°C, requiring lead length control (9.5 mm) for rated 1.0 W dissipation.

Key Specifications

Pinout & Package

DO-41 glass axial-leaded package with cathode band marking; two-terminal unidirectional device. No functional pin numbering - anode and cathode are identified by physical band location.

Key Features

Applications

Availability

1N4737A-T is available at Aetrix Electronics and suitable for industrial power supplies, sensor interface modules, overvoltage protection circuits, and microcontroller reset networks requiring stable component supply and long-term obsolescence mitigation support.

Supply support for 1N4737A-T 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

Diodes Incorporated is a global manufacturer of discrete semiconductors and analog ICs, specializing in high-reliability components for power management, signal integrity, and protection applications.

The 1N47xxA series belongs to Diodes' legacy Zener diode product line, engineered specifically for general-purpose voltage regulation and reference functions in cost-sensitive, high-volume industrial and consumer electronics.

FAQ

What is the maximum continuous power dissipation for 1N4737A-T at 70°C ambient?

At 70°C ambient, the device must be derated from its 1.0 W rating at 25°C. Derating starts at 50°C at 6.67 mW/°C, so total reduction is (70–50) × 6.67 = 133.4 mW. Therefore, maximum continuous power is 1000 – 133.4 = 866.6 mW. This assumes leads are held at 50°C with 9.5 mm length from case per datasheet Note 1.

Is 1N4737A-T compatible with lead-free reflow soldering processes?

No - the 1N4737A-T uses Sn96.5Ag3.5 termination optimized for wave and hand-soldering, not lead-free reflow. Its glass DO-41 package lacks thermal mass tolerance for peak reflow temperatures ≥260°C. For SMT-compatible alternatives, consider surface-mount Zeners like BZX84-C7V5 or MMBZ5236B.

How does the +0.02 to +0.065 %/°C temperature coefficient affect regulation accuracy?

Over a 100°C range (e.g., –25°C to +75°C), the Zener voltage shift is 7.5 V × (0.0002 to 0.00065) × 100 = +15 mV to +48.75 mV. This translates to ±0.2% to ±0.65% additional error beyond initial ±5% tolerance - critical in precision references but acceptable in general-purpose clamping.

Can 1N4737A-T replace 1N4736A (6.8 V) or 1N4738A (8.2 V) in existing designs?

No direct substitution is recommended. The 7.5 V rating lies between those parts, and Zener impedance, test current, and tempco differ significantly. Swapping changes regulation point, loop gain, and thermal drift behavior - redesign validation is required. Use only if circuit tolerances accommodate ±0.7 V shift and altered dynamic response.