1N4747CPE3/TR8

A 1N4747CPE3/TR8 diode is a single-part type of Zener diode, typically used in applications such as encoders, amplifiers, high-speed circuits and many other microelectronic applications. Zener diodes are designed to limit the voltage applied to a circuit, providing protection against over-voltage, and generally operate in a reverse-biased mode. In this scenario, current passes through the diode in the opposite direction to the normal anode-cathode current flow.

The main objective of a single 1N4747CPE3/TR8 diode is to monitor the DC voltage level and if the voltage level rises due to overvoltage, the diode “clamps” the voltage at the set zener voltage value. As the voltage increases, an increasing current also flows through the diode, which then “clamps” the voltage at the set zener voltage by dissipating the excess energy as heat.

This feature makes them suitable for numerous applications, specifically those that require protection from electrical overvoltage. They can thus be used to protect circuit components from stress caused by power-line fluctuations, load changes and even surges, as in applications such as LED lighting, LED displays, telecommunications and for stabilising supply voltage.

The 1N4747CPE3/TR8 diode usually consists of two terminal leads – anode, and cathode terminal – which are located on either side of the diode. The anode terminal is the positive terminal, and the cathode terminal is the negative terminal. When there is a reverse bias on the diode (greater potential at the cathode terminal than at the anode), a reduction in the barrier height in the p-n junction comparison occurs, and very little current passes through the diode.

When a forward bias is applied to the diode, electrons are attracted to the positively charged anode terminal. Since the current is flowing in the opposite direction, the p-n junction becomes forward-biased and the carrier electrons travel across the junction. The higher the bias and current, the stronger the effect, resulting in an increase in the voltage and a decrease in the current.

Generally, 1N4747CPE3/TR8 diodes are designed for a specific threshold voltage (Vz) and have a low leakage current. Their maximum reverse breakdown voltage ranges from 6.8V to 10V, enabling the circuit to clamp the voltage when the voltage level rises above this value. For enhanced performance characteristics, these diodes usually have a maximum peak reverse voltage of 15V.

When the reverse bias applied to a diode is the same as its zener voltage, the diode passes an equal amount of current in the forward and reverse directions. Thus, the zener voltage is ensured to remain constant through most of the range of currents and temperatures.

Zener breakdown occurs when the reverse voltage causes the p-n junction to become “pinched”, resulting in a high capacitance and therefore, an increase in the reverse current. The diode, then, operates in avalanche breakdown and the zener voltage and current become fixed. The zener voltage decreases as the current increases.

Overall, 1N4747CPE3/TR8 diodes are commonly used in several applications such as motor control, voltage regulation, attenuators, and many more applications where transient voltage protection is required. These types of diodes have excellent temperature stability (in reverse bias) and are often used as voltage clamps in high voltage, low resistance applications.