CBSE NOTES CLASS 12 PHYSICS
CHAPTER 14 SEMICONDUCTORS
The conventional method of making circuits is to choose components like diodes, transistor, R, L, C etc., and connect them by soldering wires in the desired manner. Despite the miniaturisation introduced by the discovery of transistors, such circuits were still bulky. Apart from this, such circuits were less reliable and less shock proof.
An entire circuit; consisting of many passive components like R and C and active devices like diode and transistor; on a small single block (or chip) of a semiconductor is known as Integrated Circuit (IC). The chip dimensions are very small, as small as 1nm × 1nm.
Depending on nature of input signals, IC’s can be grouped in two categories:
- Linear or analogue IC’s: The linear IC’s process analogue signals which change smoothly and continuously over a range of values between a maximum and a minimum. The output is more or less directly proportional to the input, i.e., it varies linearly with the input. One of the most useful linear IC’s is the operational amplifier.
- Digital IC’s: The digital IC’s process signals that have only two values. They contain logic gates. Depending upon the level of integration (i.e., the number of circuit components or logic gates), the ICs are termed as Small Scale Integration, SSI (logic gates < 10); Medium Scale Integration, MSI (logic gates < 100); Large Scale Integration, LSI (logic gates < 1000); and Very Large Scale Integration, VLSI (logic gates > 1000).