This article will discuss the 1N4733A 5.1V Zener diode from Onsemi, including its basics, specifications, features, circuit operation, applications, safety considerations, and more.

Catalog

1N4733A Diode Basic

The 1N4733A is a 5.1 V Zener diode is designed for reliable voltage regulation and overvoltage protection in electronic circuits. Unlike standard rectifier diodes, this device is specifically intended to operate in reverse bias, where it maintains a stable voltage once its Zener breakdown point is reached.

With a nominal Zener voltage of 5.1 V and a power dissipation rating of 1 W, the 1N4733A is well suited for low-power voltage reference applications, transistor biasing, and protecting sensitive components from voltage spikes. It comes in a DO-41 axial through-hole package, making it easy to use in prototyping, educational projects, and traditional PCB designs.

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1N4733A Diode CAD Models

1N4733A Diode Pinout Details

Alternatives & Equivalent Model

1N4733A (other manufacturers: Vishay, Nexperia, Diodes Inc.)

BZX85C5V1

BZX55C5V1

MMSZ5231B

1N5231B

TZMC5V1

ZPD5.1

BZT03C5V1

1N4733A Diode Specifications

1N4733A Diode Features

Stable 5.1 V Zener Voltage

The 1N4733A provides a nominal Zener voltage of 5.1 V, which is ideal for voltage regulation and reference applications. This voltage level is especially popular because it offers good temperature stability, helping circuits maintain consistent performance under changing conditions.

1 W Power Dissipation Capability

With a maximum power dissipation of 1 W, the diode can safely handle moderate power levels. This makes it suitable for low- to medium-power regulation circuits without requiring additional heat-sinking in most designs.

Low Zener Impedance

A typical Zener impedance of around 7 Ω ensures better voltage regulation. Lower impedance means the output voltage remains more stable even when the load current changes, improving overall circuit reliability.

Wide Operating Temperature Range

The diode operates from −65 °C to +200 °C, allowing it to perform reliably in harsh environments. This wide range makes it suitable for industrial, automotive, and outdoor electronic applications.

DO-41 Through-Hole Package

The axial DO-41 package is mechanically robust and easy to handle. It is well suited for through-hole PCBs, prototyping, and applications where durability and manual assembly are important.

Low Reverse Leakage Current

A low reverse leakage current helps minimize power loss when the diode is below its Zener breakdown voltage. This improves efficiency and protects sensitive circuit components.

RoHS Compliant Construction

The 1N4733A meets RoHS requirements, ensuring it is environmentally friendly and suitable for use in modern, regulation-compliant electronic products.

1N4733A Working in Circuit

1N4733A as a Basic Zener Voltage Regulator

In the first circuit, the 1N4733A is used as a simple shunt voltage regulator. A DC source supplies about 7.3 V, which is higher than the Zener voltage of the diode. The series resistor limits the current flowing into the Zener diode and the load. Once the voltage at the Zener reaches approximately 5.1 V, the diode enters reverse breakdown and starts conducting, clamping the voltage at that node. Any excess voltage is dropped across the resistor, while the output voltage measured across the Zener remains relatively constant. This setup demonstrates the basic principle of Zener regulation: maintaining a stable output voltage despite a higher input voltage.

1N4733A for Overvoltage Protection and Signal Clamping

In the second diagram, the 1N4733A is used to protect a low-voltage input pin (such as an ESP32 GPIO) from a much higher external voltage. A resistor divider reduces the incoming voltage, but the Zener diode provides an extra safety layer. When the node voltage tries to rise above 5.1 V, the Zener conducts and clamps it, preventing dangerous overvoltage from reaching the sensitive microcontroller input. This ensures that even if the input voltage fluctuates or spikes, the signal remains within a safe range before being further conditioned by a level shifter.

1N4733A with Load Regulation

In the third circuit, the Zener diode is placed in parallel with a load resistor. The series resistor limits current from the supply, while the 1N4733A stabilizes the voltage across both itself and the load. As long as sufficient current is available, the Zener maintains around 5.1 V across the load. If the load current changes, the Zener current automatically adjusts to keep the voltage nearly constant. This example highlights how the 1N4733A works in practical regulation scenarios where both voltage stability and load sharing are required.