When you need to buffer the output of an R-2R ladder or an RC filtered PWM signal, an op-amp is a single chip option. Unlike a discrete NPN transistor like a 2n3904, there is a lot going on inside of an LM741—or any op amp for that matter.
What if you could look inside of the op-amp? Wouldn’t it be cool to see how many transistors make up these small chips?
Put your electron microscope away. The XL741 from Evil Mad Scientist Labs is perfect for the job. I built one of these super fun solder kits and compared it to a real 741.