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I ask this question, just out of curiosity. In this die of 556 IC, what are the wave-like squiggle at the four corners, and two more on the top?

enter image description here

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Awesome! We need more semiconductor design questions here. –  Connor Wolf Mar 25 at 4:18

2 Answers 2

up vote 10 down vote accepted

Those are high-current NPN transistors. Here, from the designer's book:

enter image description here

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Great! I never would have guessed that. –  Arjob Mukherjee Mar 24 at 16:06
    
Book downloads are broken, so here's a direct link: designinganalogchips.com/_count/designinganalogchips.pdf –  GeorgeH Mar 25 at 20:36
    
Thanks, George, the book is excellent (and free) unless you insist on the print version. –  Spehro Pefhany Mar 27 at 15:37

Those are the large transistors required to drive the output pins: two for each of the totem-pole main outputs and one for each of the open-collector discharge pins. Those transistors need to handle on the order of 200 mA each, so they need to be much larger than the internal analog/logic transistors.

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