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?
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\$\begingroup\$ Awesome! We need more semiconductor design questions here. \$\endgroup\$– Connor WolfCommented Mar 25, 2014 at 4:18
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2 Answers
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Those are high-current NPN transistors. Here, from the designer's book:
answered Mar 24, 2014 at 15:48
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\$\begingroup\$ Great! I never would have guessed that. \$\endgroup\$ Commented Mar 24, 2014 at 16:06
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\$\begingroup\$ Book downloads are broken, so here's a direct link: designinganalogchips.com/_count/designinganalogchips.pdf \$\endgroup\$– GeorgeCommented Mar 25, 2014 at 20:36
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\$\begingroup\$ Thanks, George, the book is excellent (and free) unless you insist on the print version. \$\endgroup\$ Commented Mar 27, 2014 at 15:37
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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.
answered Mar 24, 2014 at 15:47