Reverse-engineering a vintage power supply chip from die photos

.hilite {cursor:zoom-in} a:link img.hilite, a:visited img.hilite { color: #fff;} I recently did a PC power supply teardown so I figured it would be interesting to go deeper and see what happens inside the power supply's control IC. The die photo below shows the UC3842 chip, which was very popular in older PC power supplies.1 (The chip was introduced in 1984 but this die has a date of 2000.) The tiny silicon die is patterned to create the transistors, resistors and capacitors that make up t...