When designing transistor amplifiers, it's necessary to have DC offsets in order to bias the transistor in the correct region of operation (forward active, not cut-off). But then the signal to be amplified is typically AC, so we need to combine AC with DC. This video shows how that is done. Then, I also explain how to extract an AC signal from a mixed AC + DC voltage in order to handle the output.

Aaron Danner is a professor in the Department of Electrical and Computer Engineering at the National University of Singapore.
https://danner.group

Video filmed and edited by Cheryl Lim.
@randomcheryl