Hybrid IC or Multichip IC
As the name implies, the circuit is fabricated by interconnecting a number of individual chips. The active components are diffused transistors or diodes. The passive components may be a group of diffused resistors or capacitors on a single chip or they may be thin-film components. Wiring or a metallized pattern provides connections between chips. Hybrid ICs are widely used for high power audio-amplifier applications from 5 W to more than 50 W. The structure of a hybrid or multichip IC is shown in fig 1.
Like thin- and thick-film ICs, hybrid ICs usually have better performance than monolithic ICs. Although the process is too expensive for mass production, multichip techniques are quite economical for small quantity production and are more often used as prototypes of monolithic ICs.
Based upon the active devices employed the ICs can be classified as bipolar ICs using bipolar active devices (BJTs) and unipolar ICs using unipolar active devices like FETs.
Level of integration in ICs has been increasing ever since they were developed few decades ago. The number of electronic circuits or components that can be accommodated into a standard size IC has been dramatically increasing with each passing year.
Classified according to their mode of operation, ICs are of two types :
- Linear IC
- Digital IC
Linear ICs are also referred to as analog ICs because their inputs and outputs can take on a continuous range of values and outputs are generally proportional to the inputs. In comparison to digital ICs, use of Linear ICs is much less but Linear ICs are quickly displacing their discrete circuit counterparts in many applications because of their lower cost and much higher reliability. Linear ICs find wide use in military and industrial applications as well as in consumer products. They are frequently used in operational amplifiers (op-amps), small-signal amplifiers, power amplifiers, RF and IF amplifiers, microwave amplifiers, voltage comparators, multipliers, voltage regulators, etc. Operational amplifier is by far the most versatile form of a Linear IC.
Digital circuits are primarily concerned with only two levels of voltage (or current) :”high” and “low”. Therefore, accurate control of operating-region characteristics is not required in digital circuits, unlike in linear circuits. That is why, digital circuits are easy to design and are produced in large quantities as low-cost devices. About 80% of the IC market has been captured by digital ICs which are mostly utilized by the computer industry. Digital ICs lend themselves easily to monolithic integration because a computer makes use of a large number of identical circuits. Moreover, such circuits make use of relatively few capacitors and values of resistances, voltages and currents are low. Sometimes, digital circuits are referred to as switching circuits. They find wide application in computers and logic circuits. Digital ICs include circuits like logic gates, flip-flops, counters, clock chips, calculator chips, memory chips, and microprocessors.