By its very nature, digital has always led analog in the level of integration possible at any point in time. Jack Kilby’s first device, after all, was a digital circuit.
It is clear that this trend towards higher levels of integration is continuous. I believe, however, we are in a period in this evolution of analog integration that moves us into a new era.
Integration started out quite simply: the op-amp. Bob Widlar developed the first integrated op-amp, the uA702 at Fairchild in 1963. It was not very popular due to various quirks. In 1965, he developed the uA709, which integrated, I believe, 14 transistors and 15 resistors. The ’709 was very successful and the race was on.
The main drawback of the ’709 was that it had to be compensated (stabilized) with an external capacitor. In 1968, Dave Fullagar, also at Fairchild, developed the internally compensated uA741 op amp. The ’741 had a few more transistors and resistors than the ’709, but the key difference was that it also integrated a capacitor that compensated the device.
Analog circuits became more complex over the following years, but analog ICs were all of the “building block” type. Some ICs did manage to combine a couple of similar building blocks. The next step was to integrate dissimilar functions in one IC.
Perhaps the most famous of the early ICs to integrate dissimilar functions is the MAX232. The idea for this part came from Charlie Allen of Maxim, whom Fullagar once described as “the best applications engineer I have ever encountered.” Charlie noticed that a lot of equipment was operating completely from 5V supplies, except for the RS-232 drivers, which required ±12V supplies. If an RS-232 chip could be made to run from 5V, then the equipment makers could eliminate these two supply rails. In 1987, Dave Bingham designed the MAX232, integrating charge pumps, a type of DC-DC converter, to generate the larger voltages needed for the RS-232 drivers.
Over time, this integration of dissimilar functions has increased. Equipment designers have benefited, as their designs require fewer circuits, can be developed more quickly, and are smaller and less expensive.
So why do I say we are entering a new era in analog integration? As the number of dissimilar functions integrated in a single IC increases, we are now seeing circuits that integrate so much that they take up a major portion of the end equipment.
While earlier analog ICs were developed to provide certain functions that could be used in a number of end equipment types, these more highly integrated components are targeted to specific single applications.
Much of the system architecture is now in the chip, and the chip manufacturers now have to be experts in the end equipment and work very closely with the makers of the equipment.
This is fundamentally different than the days where all analog ICs were building blocks. As with integration in general, this trend will continue toward higher and higher levels of integration.