Impedance bridging
In electronics, especially audio and sound recording, a high impedance bridging, voltage bridging, or simply bridging connection is one in which the load impedance is much larger than the source impedance. In cases where only the load impedance can be varied, maximizing the load impedance serves to both minimize the current drawn by the load and maximize the voltage signal across load. Essentially, the load is measuring the source's voltage without affecting it. In cases where only the source impedance can be varied, minimizing the source impedance serves to maximize the power delivered to the load. A different configuration is an impedance matching connection in which the source and load impedances are either equal or complex conjugates. Such a configuration serves to either prevent reflections when transmission lines are involved, or to maximize power delivered to the load given an unchangeable source impedance.
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When the output of a device (consisting of the voltage source VS and output impedance ZS in illustration) is connected to the input of another device (the load impedance ZL in the illustration), it is a bridging connection if the input impedance of the load device is much greater than (typically at least ten times) the output impedance of the source device.
Given an unchangeable ZS, one can maximize the voltage across ZL by making ZL as large as possible. This also correspondingly minimizes the current drawn from the source device. This has a number of effects including:
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