Semiconductors and Diodes

Transistors, including PNP types, are manufactured using semiconductor materials like silicon or germanium.

A TRIAC (Triode for Alternating Current) acts as a bidirectional switch, allowing current to flow in both directions, similar to two SCRs connected in anti-parallel.

MOSFET stands for Metal-Oxide-Semiconductor Field-Effect Transistor. The 'E' stands for Effect.

Germanium doped with phosphorus is an example of n-type semiconductor. Silicon and germanium are group 14 elements having four valence electrons. In their crystals, each atom forms four covalent bonds with its neighbours. When doped with a group 15 element like P or As, which contains five valence electrons, they occupy some of the lattice sites in silicon or germanium crystal. Four out of five electrons are used in the formation of four covalent bonds with the four neighbouring silicon atoms. The fifth electron is extra and becomes delocalised. These delocalised electrons increase the conductivity of doped silicon or germanium. Here, the increase in conductivity is due to the negatively charged electron, hence silicon or germanium doped with electron-rich impurity are called n-type semiconductors.

Second-generation computers (roughly 1956-1963) replaced vacuum tubes with transistors, which are semiconductor devices used to amplify or switch electronic signals.

Doping of silicon ( Si ) with boron ( B ) leads to p - type semiconductor.

ANS 4.

Transistors are smaller, consume less power, and are faster than vacuum tubes. Since all options A, B, and C are indeed merits of transistors, 'None of these' is the correct choice because there is no incorrect merit listed.

Gallium arsenide (GaAs) is a compound of the elements gallium and arsenic. It is a III/V semiconductor, and is used in the manufacture of devices such as microwave frequency integrated circuits, monolithic microwave integrated circuits, infrared light-emitting diodes, laser diodes, solar cells, and optical windows.

VT is a function of several components, most of which are material constants such as the difference in work-function between gate and substrate material, the oxide thickness, the Fermi voltage, the charge of impurities trapped at the surface between channel and gate oxide, and the dosage of ions implanted for threshold adjustment. From the above arguments, it has become clear that the source-bulk voltage VSB has an impact on the threshold as well. Therefore, whenever there is an increase in the source-bulk voltage, threshold voltage also increases. 

An operational amplifier (op-amp) is an integrated circuit consisting of many transistors, resistors, and capacitors designed to perform mathematical operations.

Analog circuits are circuits dealing with signals free to vary from zero to full power supply voltage. This stands in contrast to digital circuits, which almost exclusively employ 'all or nothing' signals. Both the input and output signals are analog here.