输出阻抗（英语：output impedance），或称内阻（internal impedance），是指电路负载从电路输出端口反着看进电路时电路所等效的阻抗。

• Calculation of the damping factor and the damping of impedance bridging

The output impedance, source impedance, or internal impedance of an electronic device is the opposition exhibited by its output terminals to an alternating current (AC) of a particular frequency as a result of resistance, inductance and capacitance. It is the Thévenin equivalent impedance looking back into the output terminals.