Delete comment from: Ken Shirriff's blog

bite said...

Hi,

I'm glad to see some analog IC reverse engineering stuff.
Last year, i tried to reverse the ne556 (there is a nice picture of it from zeptobar: http://zeptobars.com/en/read/stm-ne556-555) and i wasnt able to identify transistor type (pnp/npn). I had no clue for that, so i just ignored the type then tried to eliminate the "impossibru" design with hypothesis (yeah, painful).
As far as i known the circular shape of emitter is for compensating device mismatch between transistors. NPN can also have circular emitter. Or am i wrong?

Btw, the device layout of Q21 looks like a diode?
For me, this shit looks like that

Feb 23, 2016, 5:55:32 PM

Posted to 555 timer teardown: inside the world's most popular IC