PART FINDER FRIDAY – LOGIC CHIPS. Whenever you have 3.3V logic and you want to interface it with 5V logic, you need to take care so that you don’t shove 5V into a 3V input. We’ve found an easy way to do that is to use a level shifter such as a 74AHC125 or CD4050. The ’125 has 4 buffers and can be tri-stated, the 4050 has six buffers. Both can take 5V input on any pin if the chip is powered with 3V so effectively it converts down. Much faster than using resistors (almost no slewing) and works even if you end up using 3V on both sides. A good example of this is in our oled breakout board which is a 3V part, but easily wired up to talk to an Arduino which is 5V.