Any driver on a circuit that has a non-zero output [Impedance] requires ImpedanceMatching to deliver the maximum amount of power to the load. 

  

 If the load InputImpedance (resistance) is equal to the drivers OutputImpedance, the power at the load is at a maximum. If there is a TransmissionLine connecting the driver to the load, it must also have a CharacteristicImpedance close to the OutputImpedance, so as to instantaneously load the driver to the right load, to prevent ringing in the circuit. Imagine you take a TransmissionLine and make an incision, both sides of the TransmissionLine will be the same CharacteristicImpedance as the original line. This can be modeled as a amplifier with unity gain (0dB) and an InputImpedance and OutputImpedance equal to the CharacteristicImpedance of each respective side, ensuring maximum power is transferred.