onsemi 1N5994B_T50A

Overview

1N5994B_T50A from Fairchild Semiconductor is a 5.6 V, ±5% tolerance Zener diode in DO-35 glass package, rated for 500 mW power dissipation at TL ≤ 75°C with 4.0 mW/°C derating, 25 Ω zener impedance at 5 mA test current, and 2 mA leakage current at 3 V reverse voltage. It serves as a precision voltage reference or overvoltage clamp in low-power analog circuits.

For engineers reviewing the 1N5994B_T50A datasheet, pinout, applications, or equivalent options, this page delivers verified electrical parameters, thermal limits, DO-35 terminal mapping, and direct alternatives for voltage regulation design in industrial sensors, power supply feedback loops, and signal conditioning stages.

Technical Context

The 1N5994B_T50A operates as a silicon planar Zener diode with sharp reverse breakdown at nominal 5.6 V, designed for stable voltage regulation under DC bias conditions. Its 25 Ω dynamic impedance at 5 mA ensures minimal output voltage variation across load changes in shunt regulator configurations.

Thermal performance is defined by a -65°C to +200°C operating/storage range and 4.0 mW/°C linear derating above 75°C lead temperature, requiring attention to PCB copper area and lead length (3/8″ specified) for reliable power handling. The device exhibits 2 mA leakage at VR = 3 V, confirming tight low-voltage blocking integrity.

Key Specifications

Pinout & Package

DO-35 glass axial package with cathode indicated by color band; leads are non-polarized terminals with no internal asymmetry beyond cathode marking.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 1N5994B_T50A, the 1N4734A offers lower impedance but demands higher bias current, while the BZX55-C5V6 delivers dramatically lower leakage and tighter regulation-making both suitable for upgraded performance tiers where 1N5994B_T50A's cost-effective 25 Ω/2 mA trade-off is insufficient.

Availability

1N5994B_T50A is available at Aetrix Electronics and suitable for industrial sensor interfaces, microcontroller power rail protection, and linear regulator feedback networks requiring stable component supply across extended temperature ranges.

Supply support for 1N5994B_T50A 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, analog, and discrete components before its acquisition by ON Semiconductor in 2016.

The 1N59xxB series was engineered for general-purpose Zener regulation in cost-sensitive industrial and consumer electronics, emphasizing reliability, wide temperature operation, and DO-35 compatibility with legacy designs.

FAQ

What is the nominal Zener voltage and tolerance of the 1N5994B_T50A?

The 1N5994B_T50A has a nominal Zener voltage of 5.6 V with a guaranteed tolerance of ±5%, meaning the actual breakdown voltage falls between 5.32 V and 5.88 V when tested at 5 mA. This specification is measured under thermal equilibrium at 30°C ±1°C lead temperature with 3/8″ lead length, per Fairchild's Rev. C2 datasheet. The 1N5994B_T50A maintains this tolerance across its full operating temperature range.

What is the maximum power dissipation and thermal derating behavior of the 1N5994B_T50A?

The 1N5994B_T50A is rated for 500 mW power dissipation at a lead temperature (T_L) of ≤75°C. Above 75°C, it derates linearly at 4.0 mW/°C. This means at 100°C lead temperature, its usable power drops to 400 mW. The derating curve assumes 3/8″ lead length and requires adequate PCB copper area for heat sinking. The 1N5994B_T50A's -65°C to +200°C operating range allows use in extreme thermal environments when power is managed accordingly.

What is the Zener impedance of the 1N5994B_T50A and why does it matter?

The 1N5994B_T50A exhibits a Zener impedance (Z_Z) of 25 Ω at the 5 mA test current. This value represents the dynamic resistance in the breakdown region and directly affects voltage regulation accuracy: a lower Z_Z yields smaller output voltage shifts under varying load current. For example, a 10 mA load change causes ~250 mV variation across the 1N5994B_T50A. Engineers use this parameter to size series resistors and assess suitability for precision reference versus coarse clamping roles in their circuit using the 1N5994B_T50A.

How is the cathode identified on the 1N5994B_T50A DO-35 package?

The cathode of the 1N5994B_T50A is marked by a distinct color band on the DO-35 glass body, consistent with industry-standard polarity marking. The anode is the unmarked lead. This band must be oriented toward the higher-potential node in reverse-biased Zener operation. The 1N5994B_T50A's top marking consists of "F" (Fairchild logo), "99", and "4B" on three lines, with the cathode band serving as the sole functional polarity indicator-not the marking layout. Correct orientation is essential to avoid forward conduction failure.

What is the leakage current specification for the 1N5994B_T50A and under what condition is it measured?

The 1N5994B_T50A has a maximum leakage current (I_R) of 2 mA when subjected to a reverse voltage (V_R) of 3 V at 25°C. This parameter reflects off-state conduction below the Zener knee and impacts high-impedance circuit nodes-such as op-amp inputs or microcontroller reset lines-where even microamp-level leakage could cause errors. The 1N5994B_T50A's 2 mA value is significantly higher than ultra-low-leakage alternatives like BZX55-C5V6 (100 nA), making it appropriate for moderate-impedance applications but unsuitable for nanoamp-sensitivity designs.