How an Integrated Circuit Works

A well-known saying suggests that there are no bad students, only bad teachers. And when it comes to learning electronics, it’s essential to find someone who can explain beyond books, theories, and values. At the 2019 Maker Faire Bay Area, the team from Evil Mad Scientist Labs did an extraordinary job teaching and demonstrating the workings of the first commercial integrated circuit, the Fairchild μL914. If you want to know more about transistors, resistors, and how an integrated circuit works, you need to see this.

If you've ever wondered what’s inside an integrated circuit, you’re not alone. Beyond official diagrams, the alternative is to strip the chip and place it under a microscope, a task that is far from simple.

However, some experts and enthusiasts who passed through the Maker Faire Bay Area (which concluded last Sunday) took that question and turned it into a brilliant educational session. Windell Oskay, Lenore Edman, Eric Schlepfer, John McMaster, and Ken Shirriff combined their efforts in an exhibition that demonstrates with great precision how an integrated circuit works.

This is How an Integrated Circuit Works

The chip chosen was a Fairchild μL914, and it’s no coincidence. On one hand, it is the first commercial integrated circuit, and on the other, its size and age (it was released in the ’60s) make it easier to 'open' so to speak. The μL914 is what is known as a dual two-input NOR gate, while in real life it looks like a small spider.

With the help of a small box and a couple of LED lights, it’s very easy to demonstrate the circuit’s operation. The output of a NOR gate remains 'high' or 'on' as long as the condition of its two inputs is 'low' or 'off'. If one of them or both change, the input will be 'low', turning off the LED light. Pins 1 and 2 are the inputs of gate A, pins 3 and 5 are the inputs of gate B, pins 7 and 6 correspond to outputs A and B, pin 8 is V+, and pin 4 is ground.

The team managed to remove the epoxy that covers the chip, and placing it under the microscope it’s possible to observe its internal design, but that’s not all. Oskay shows us in the video a large-scale plastic version of an NPN transistor, the same one we detect inside the μL914, with references to its base, emitter, and collector.

The best part is the 3D acrylic model of the Fairchild μL914. Its six transistors are exposed, and the 'dog bones' are actually resistors. Pins 1 and 2 pass through the resistors and connect to the bases of two transistors. The emitters of those transistors are connected together, and from there they go to pin 4 which is ground. The same happens with the collectors, but their destination is pin 7. And the process repeats with pins 3 and 5.

Another aspect to highlight is that the Fairchild μL914 has redundant components. The transistors are 6, but it only uses 4 (one is shorted, and one 'floating'). Also a couple of resistors are left over.

In summary, a fabulous job by this team. If all electronics were like this, it wouldn’t be so complicated to grasp its concepts. Want more? Don’t hesitate to read our articles on circuit simulators and how servomotors work.

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