Long-tailed pair

A differential amplifier is a type of electronic amplifier that amplifies the difference between two input voltages but suppresses any voltage common to the two inputs. It is an analog circuit with two inputs ${\displaystyle \scriptstyle V_{\text{in}}^{-}}$ and ${\displaystyle \scriptstyle V_{\text{in}}^{+}}$ and one output ${\displaystyle \scriptstyle V_{\text{out}}}$ in which the output is ideally proportional to the difference between the two voltages

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