The **1N4747A** is a Zener diode with a specified Zener voltage of **20 volts**. Zener diodes are semiconductor devices that are designed to maintain a constant voltage across their terminals when operated in the reverse breakdown region, which is known as the Zener breakdown voltage. Here are some key details about the 1N4747A Zener diode:
1. **Zener Voltage (Vz):** The primary characteristic of the 1N4747A is its Zener voltage, which is 20 volts. This means that when the diode is connected in reverse bias and the voltage across its terminals reaches 20 volts, it will regulate and maintain this voltage, acting as a voltage reference.
2. **Reverse Breakdown Voltage:** The 1N4747A will start conducting in the reverse direction (reverse bias) when the voltage across its terminals reaches or exceeds the Zener voltage of 20 volts. It allows current to flow in this reverse direction to maintain the specified voltage.
3. **Power Dissipation:** The diode is rated for a certain power dissipation, which indicates the maximum power it can safely dissipate as heat without getting damaged. The power dissipation for the 1N4747A typically ranges from 1.0 watt.
4. **Tolerance:** Zener diodes often have a specified tolerance for their Zener voltage. For example, a 20V Zener diode might have a tolerance of ±5%, which means that the actual Zener voltage could be between 19V and 21V.
5. **Package Type:** Zener diodes like the 1N4747A are available in various package types, such as through-hole packages (like the DO-41 package) and surface-mount packages. The package type influences how the diode is physically mounted on a circuit board.
6. **Applications:** Zener diodes are commonly used as voltage regulators, voltage references, and in overvoltage protection circuits. They are frequently used in power supplies and electronic circuits where a stable and constant voltage is required.
7. **Datasheet:** It’s essential to refer to the datasheet for the specific 1N4747A component you have for detailed electrical characteristics, maximum ratings, and application information.
When using a Zener diode like the 1N4747A in your circuit, ensure that it is properly connected in reverse bias with a current-limiting resistor. This helps maintain a stable voltage across its terminals and prevents excessive current flow that could damage the diode. The Zener voltage rating should match the desired voltage regulation level for your application.