Semiconductor Devices: Diodes, Thyristors, and Transistors
Bias
In this polarization, negative atoms are attracted by the positive, and the negative by the positive, i.e., there would be a reversal of the current.
Zener Diode
This type of diode works like a normal one, but when reverse biased, it allows current to flow from a particular value of the bias voltage. This diode has a stabilizing function when the value of this variable exceeds the reverse bias. Conduction occurs in the opposite direction to establish a current through the Zener, and the resistance causes a voltage drop. It has an appropriate protection function when a consumer device is subjected to significant tension variations and can be protected with a Zener diode.
LED Diode
A special type of diode used in automotive applications. It emits light when a small electric current travels through it. The use of LEDs is very common in the dashboards of cars for signaling.
Thyristor
A semiconductor consisting of four alternating silicon crystals, two to two, with P and N polarities. It can be considered as a combination of two independent transistors.
Circuit Explained
The anode is connected to the main power source through the switch, but even if it is closed, the thyristor does not lead until it receives the control pulse at the gate. This impulse may be provided by the auxiliary voltage source, which connects instantly. Even if it disconnects, the thyristor conducts until the supply current is continuously cut through the switch, and it remains blocked. Even if the switch is re-closed, the thyristor does not conduct and requires a new trigger pulse at its gate to return to the state of conduction.
Transistor
An electronic element formed by the union of two diodes in opposition, capable of regulating the passage of electric current in a circuit. It comprises three consecutive semiconductor regions of type P and N. There are two types of transistors: NPN and PNP. Each of the three semiconductor regions has a connection. The central region is called the base, and the two exterior regions are the emitter and collector. The transistor has a function similar to a relay, controlling high currents through other smaller ones. The base acts as an insulating barrier between the other two, so there is no transportation of currents between the emitter and collector while no voltage is applied to the base.
In the PNP transistor, the base current flows in the emitter-base sense, and the mainstream does it in the emitter-collector sense. While in the NPN transistor, the senses of both currents are contrary to earlier reports, although the operation is the same.
Advantages of a Transistor Relay
- The transistor is lighter.
- Mobile contacts are deleted.
- They are subject to normal wear due to their own operation.
- Breakdowns are deleted in the transistor.
Electrolysis
SO4 anions, negatively charged, have excess electrons and are directed toward the anode to download the leftovers there. When they have no electric charge, they become atoms and ions to react with water molecules that are in the neighborhood, stealing the hydrogen (H2) to form an acid molecule again. The oxygen left of the water molecule as an ion is an atom but is apparent at the anode in the form of bubbles.