The input impedance or load impedance of a circuit or electronic device is the impedance actually experienced by a signal which is connected to it.

For example, an amplifier with 100,000 ohm input impedance looks equivalent to a 100,000 ohm resistor to the signal coming into it.

Generally in audio and hi-fi, the input impedance of components is several times higher than the output impedance connected to them. This is called voltage bridging or impedance bridging. In this case,

Z_load >> Z_source

In video and other systems the impedance of inputs and outputs are the same. This is known as impedance matching or a matched connection. In this case,

Z_load = Z_source

See also

• Impedance
• Output impedance
• Source impedance
• internal impedance
• Damping factor
• Voltage divider
• Dummy load

External links

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