The word ‘monolithic’is derived from the Greek monos, meaning ‘single’and lithos, meaning ‘stone’. Thus monolithic circuit is built into a single stone or single crystal i.e. in monolithic ICs, all circuit components, (both active and passive) and their interconnections are formed into or on the top of a single chip or silicon as shown in fig. 1 (a) and (b).
Fig 1 (a) : Monolithic IC in Can-Type Enclosure
Fig 1 (b): Monolithic IC in Plastic Package
Advantages of Monolithic ICs
- Miniature in size. Since the active and passive components are integrated on to a silicon chip using fabrication process , the IC becomes a lot smaller. When compared to a discrete circuit, it may be at least a thousand times smaller.
- Due to small size, the weight of the IC also reduces, when compared to the discrete circuit.
- For the production of hundreds of IC’s the cost of production is very low and less time consuming. However, to produce hundreds of discrete circuits on a PCB for the same logic takes more time and increase the cost factor.
- The PCB consisting soldered joints will be less reliable. This problem is omitted in IC’s because of no soldered joints, with fewer interconnections, and thus highly reliable.
- The small size of IC’s causes lesser power consumption and lesser power loss.
- In a discrete circuitry, if a single transistor becomes faulty, the whole circuit may fail to work. This transistor has to be desoldered and replaced. It is difficult to find out which component has failed. This problem can be omitted in an IC by replacing an entire IC as it is low in cost.
- Increased operating speed because of absence of parasitic capacitance effect.
- As the IC’s are produced in bulk the temperature coefficients and other parameters will be closely matching.
- Improved functional performance as more complex circuits can be fabricated for achieving better characteristics.
- All IC’s are tested for operating ranges in very low and very high temperatures.
- As all the components are fabricated very close to each other in an IC, they are highly suitable for small signal operation, as there won’t be any stray electrical pickup.
- As all the components are fabricated inside the chip, there will not be any external projections.
Since their invention, manufacturers have been manufacturing monolithic ICs to carry out all types of functions. Commercially available ICs of this type can be used as amplifiers, voltage regulators, crowbars, AM receivers, TV circuits and computer circuits.
Disadvantages of Monolithic ICs
However, the monolithic circuits have the following limitations or drawbacks:
- Low power rating. Since monolithic ICs are of about the size of a discrete small signal transistor, they typically have a maximum power rating of less than 1 watt. This limits their use to low-power applications.
- Poorer isolation between components.
- No possibility of fabrication of inductors.
- Small range of values of passive components used in the ICs.
- Lack of flexibility in circuit design as for making any variation in the circuit, a new set of masks is required.