https://blog.gongquiz.com/2023/01/24/%eb%8b%a4%ec%9d%8c-%ec%a4%91-%ec%b0%a8%eb%8f%99%ec%a6%9d%ed%8f%ad%ea%b8%b0differential-amplifier%ec%9d%98-%ed%8a%b9%ec%a7%95%ec%97%90-%eb%8c%80%ed%95%9c-%ec%84%a4%eb%aa%85%ec%9c%bc%eb%a1%9c/