integrated circuits (ICs) are a keystone of modern electronics. They are the heart and brains of most circuits . An IC can function as an amplifier, oscillator, timer, counter, computer memory, or microprocessor. An IC is also called a chip or microchip, is a semiconductor wafer on which thousands or millions of tiny resistors, capacitors, and transistors are fabricated. The integration of large numbers of tiny transistors into a small chip results in circuits that are orders of magnitude smaller, cheaper, and faster than those constructed of discrete electronic components. The resulting circuit is thus a small monolithic “chip, ” which may be as small as a few square centimetres or only a few square millimetres. The individual circuit components are generally microscopic in size. Linear IC, Digital IC, Analog IC Memory IC, CPU ROM, RAM, DRAM, SDRAM, NAND, EPROM, EEPROM Obsolete and Hard to find ICs ICs come in various packages, most common are DIP (dual-in-line), SIP (single-in-line), SMD (Surface mounted device), PLCC, TSSOP, SOIC, TSOP, QFP, PQFP, LCC, etc.