Why are the capacitors so big, while the transistors are tiny?
In: Technology
A capacitor is a non-conductive material sandwiched between two conductors. So you have three layers to start with. But the more capacitance you want, the more surface area you need. This surface area is increased by increasing the length and width of the sandwich. A small value capacitor might be no bigger than a fingernail. But a large value capacitor might have many feet of this sandwich all wrapped up into that container.
Generally, the higher the voltage a capacitor must handle, the thicker the sandwich must be. So a high voltage, but low capacitance capacitor can be the same size as a low voltage, but high capacitance capacitor.
This is in contrast to a transistor, which is just three microscopic dots on a chip of silicon or germanium. The closer these dots are to each other (without mixing together), the more efficient the transistor becomes (generally). But high voltage or current requirements also force us to make the dots bigger to handle it. Even so, these dots are still microscopic, and the packaging is large to handle the heat power transistors generate.
Tl;Dr: electrons are meant to cross a barrier in transistors. The smaller the barrier, the more efficient the transistor. Voltage is never meant to cross the barrier in a capacitor, so the barrier must be comparatively huge. High capacitance requires lots of surface area, and high voltages require thick barriers – each makes a capacitor very large compared to a transistor.
There’s a lot more that goes into the engineering of each, but I hope this is an adequate ELI5 version.
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