In this tutorial, we will learn to use 1N747 Zener Diode with example circuits. It offers a Zener voltage (Vz ) of 3.6V with ±5% tolerance and a speedy reverse recovery time. Zener diodes are used for voltage regulation applications.
Zener Diode Introduction
A diode is an electronic device that permits the current to flow only in one direction, but there is an exception to it i.e., a Zener diode. A Zener diode is a diode that acts as a two-way switch. It means that it can conduct current in forward as well as reverse direction. It is a heavily doped diode and permits the reverse current when a specific voltage level is reached.
1N747A is a typical Zener diode that finds its applications in a wide range of electronic systems, from regulators to switches to clippers because of its reverse conduction quality.
Following diagram shows the pinout of the 1N747A diode:
Just like a typical diode, this silicon planar also has two terminals. One is a positively charged anode, and the second terminal is a negatively charged Cathode.
The Zener diode is typically operated in reverse-biased condition.
|Zener diode anode pin
|Zener diode cathode pin
1N747 Features and Specifications
- Power Dissipation: 500 mW
- Forward Voltage(IF=200 mA): 1.5 Volts
- Zener Bias Current: 20 mA
- Zener Voltage: 3.6 Volts
- Max Zener Current: 100 mA
- ± 5% Zener Voltage Tolerance
- Package Type: DO-35
Some of the other features are mentioned below :
- Cutting-edge reverse characteristics
- High reverse current carrying capacity
- High reverse breakdown voltage
1N747 Example Circuits
1N747 as a Voltage Regulator/Protection Circuit
The schematic shown above is the circuit of a voltage regulator using a Zener diode.
The load is connected in parallel and reverse to the Zener diode.
A significant current begins to flow through the Zener diode whenever a voltage applied to the Zener is greater than the reverse breakdown voltage. The voltage drop across the Zener diode is slight. Even though the current surpasses as the voltage rises, the voltage across the Zener stays constant and is equal to its breakdown voltage. The voltage across the load is equal to the breakdown voltage of the zener since the load and zener are linked in parallel. It offers us two advantages. The voltage is first controlled or clipped to the reverse breakdown voltage level. Second, the diode receives the entire high current rather than the load.
In short, if we require, for example, 10 Volts across the load, then we need a Zener diode with a reverse voltage of 10 Volts.
1N747 Double Clipper Circuit
This circuit is a full-wave clipper circuit. Two Zener diodes are connected back to back to perform the clipping.
Picture Credit: electronics-tutorials
The working is the same as the circuit described before. During the positive half cycle, ZD1 will be reverse-biased and perform the clipping of the input AC wave. And when a negative cycle comes, ZD2 will be reverse biased and clip the signal up to the reverse breakdown voltage.
Practically, the voltage is clipped at the sum of Zener reverse voltage and its voltage drop.
These clipping circuits frequently find their application in Frequency Modulation Transmitters to remove voltage spikes and output a noise waveform.
1N747 Alternative Options
- Voltage Regulators
- Switching Circuits
- Power supplies
- Freewheeling diodes
- Reference Voltage
- Protection Circuits
The 1N747A comes in a DO-35 glass package. The 2d model of the diode is provided below: