Electronic Devices

Semiconductor devices are made up of semiconductor materials like germanium and silicon with semiconductor properties. For example, it partially allows electricity into it. These semiconductor devices have a wide range of applications in rectifications, ionisations, power devices, solid-state lasers, and optical sensors. Moreover, these devices are cheap, reliable, and compact. This article provides a detailed summary of electronic devices like semiconductor diodes, transistors, and logic gates, with their symbols.

Semiconductor Diode

A semiconductor diode is made up of semiconducting metals like silicon and germanium. In these diodes, we have positively charged holes and negatively charged electrons. The holes are present in the anode, and the electrons are present in the cathode. The cathode and anode are parallelly placed to each other. The anode is called the positive(+) p layer, and the cathode is called the negative(-) n layer.

PN junction diode

The P-type material and N-type material are merged to form a PN junction using the principle of the grain boundary. The P-N junction is a solid-state electronic device. The positive side of the diode has holes called as p side, and the negative side of the diode has electrons called as n side of the semiconductor. The process of doping creates these p sides and n sides.

Forward bias PN junction diode

When the (+) terminal of the battery is connected to the p-type of the semiconductor diode, and the (–) terminal of the battery is connected to the n-type, it is called forward-bias PN junction.

In a forward-bias PN junction diode, the junction electric field and applied electric field will be opposite. So, the magnitude is less than the junction electric field. As a result, it has less resistivity and a thinner depletion region.

Reverse Bias PN junction diode

When the (+) terminal of the battery is connected to the n-type of the semiconductor diode, and the (–) terminal of the battery is connected to the p-type, it is called reverse-biased PN junction bias.

The junction and applied electric fields will be in the same direction as in the reverse-biased PN junction diode. So, the magnitude is more than the junction electric field. Therefore, it has more resistivity and a thicker depletion region. As the voltage increases, the depletion region becomes resistive and thicker.

In reverse bias, there will be an increase in the potential barrier and the minority carriers’ flows in the junction, called reverse saturation current. These minority carriers increase kinetic energy, which affects majority carriers.

For silicon diodes, the barrier potential is 0.7 V, and for germanium, the barrier potential is 0.3V. The barrier potential is also called cut-in voltage or knee voltage. The reverse characteristics can be obtained by reverse biasing the PN junction diode. In the particular reverse voltage, the reverse current increases rapidly. It is called the breakdown voltage.

Transistors

A transistor is a three-terminal electronic device that transfers a signal from a low to a high resistance circuit.

Transistor has three parts : Emitter, Base, Collector.

Emitter: It is highly doped and emits the majority carrier towards the base. It is medium in size.

Base: It is lightly doped and sandwiched between the emitter and collector. It is thin in size.

Collector – It is moderately doped and collects the majority of carriers emitted by the emitter. It is large.

Types of transistors

There are mainly two types of transistors: NPN transistor or PNP transisitor.

NPN transistor

If a thin P layer of the semiconductor is sandwiched between two thick N layers, it is called NPN transistors.

PNP transistor

If a thin N layer of the semiconductor is sandwiched between two thick P layers, it is called PNP transistors.

Logic gates

The logic gates can represent the logical relationship between the input and output voltage of the circuit. The truth table is the table that indicates the operations of the logic gate and contains all the possible combinations of inputs and output.

Basic logic gates

There are three basic logic gates: AND, OR and NOT gate.

AND gate

If all the inputs are high in the AND gate, the AND gate attains the high state.

Y = A.B

The truth table of AND

OR gate

In OR gate, if one or more inputs are high , the OR gate attains the high state.

Y = A + B

Truth table of OR

NOT gate

In NOT gate, if the input is high , the NOT gate attains the low state and vice-versa.

Y = A

Truth table of NOT

Combination of logic gates

NOR gate

NOR gate is the combination of the basic gates, OR and NOT gate.

Y = A+B

Truth table of NOR

NAND gate

NAND gate is the combination of the basic gates, AND and NOT gate.

Y = A.B

Truth table of NAND

X-OR gate

If any one input attains the high state, the output of XOR attains high.

Y = AB + AB = A B

Truth table of XOR

X-NOR gate

If both the inputs are the same, the output of XNOR attains high.

Y = A.B + A B

Y = A⊕ B

Truth table of XNOR

Conclusion

In this topic, we have seen semiconductor devices used for many applications in the electronic world. Semiconductor devices are made up of semiconductor materials like germanium and silicon. Electronic devices cover three important semiconductor components: Diode, transistor, and logic gates. We have discussed the three biasing conditions of the diode and the types of the transistor. The basic and combination of logic gates were explained with the help of the truth table. These three devices play a significant role in embedded physics and electronics.