What is the best antivirus that wont slow pc down?

Hi friends, I am looking for an best antivirus for my computer, that wont slow down pc performance or slow down boot time much??

Thanks in advanced.

u can try avast..but it depends on ur ram too..if ur ram is low then it will slow ur pc down coz these days antivirus are huge due to updates..but avast is beautiful..doesnt slow ur pc..