Electronics

According to the NCERT Solutions for Class 12 Physics Chapter 14 Semiconductor Electronics, intrinsic semiconductors are pure forms of semiconductor materials with no impurities like germanium or silicon. At room temperature, their conductivity is very low because they are solely based on thermally generated charge carriers (electrons and holes). On the other hand, extrinsic semiconductors to increase the conductivity, they are doped with impurities. P-type are doped with trivalent atoms (extra holes) and N-type semiconductors are doped with pentavalent atoms (extra electrons).
Doping makes extrinsic semiconductors far more conductive by enhancing the number of charge carriers. It becomes more practical for electronic devices like transistors, diodes, and integrated circuits.

A transistor can either be NPN or PNP. It is a three-layer semiconductor device with three terminals—emitter, base, and collector.  In the case of the NPN transistor, there is a larger current from the collector to the emitter due to a small current at the base. It involves an amplification property which is key to the function of the NPN transistor. A transistor can be used in two main modes - as switches in microcontrollers, and computers and as amplifiers in speakers and radios etc. These are foundational in digital and analogue circuits due to their ability to control current. Transistors form the backbone of the integrated circuits and modern electronics.

Energy bands refer to how electrons behave in solids. In the case of conductors where the conductivity is high, the valence band and conduction band overlap which lets the electrons move freely. In the case of semiconductors, the valence and conduction bands have a small energy gap between them such as ?1 eV. There is a requirement for some external energy for electrons to jump to the conduction band. The gap is large in the case of insulators (>3 eV), making the electron movement nearly impossible. The energy band model differentiates how easily a material can conduct electricity. In semiconductors, there is controlled conductivity which is important for electronic devices as in these cases light or thermal energy can excite electrons.

According to the NCERT Solutions for Class 12 Physics Chapter 14 Semiconductor Electronics, intrinsic semiconductors are pure forms of semiconductor materials with no impurities like germanium or silicon. At room temperature, their conductivity is very low because they are solely based on thermally generated charge carriers (electrons and holes). On the other hand, extrinsic semiconductors to increase the conductivity, they are doped with impurities. P-type are doped with trivalent atoms (extra holes) and N-type semiconductors are doped with pentavalent atoms (extra electrons).
Doping makes extrinsic semiconductors far more conductive by enhancing the number of charge carriers. It becomes more practical for electronic devices like transistors, diodes, and integrated circuits.