In audio engineering 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. The load measures the source's voltage while minimally drawing current or affecting it.
Explanation
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When the output of a device (consisting of the voltage source V<sub>S</sub> and output impedance Z<sub>S</sub> in illustration) is connected to the input of another device (the load impedance Z<sub>L</sub> in the illustration), these two impedances form a voltage divider:
:<math>
V_L = \frac{Z_L}{Z_S + Z_L} V_S \, .
</math>
One can maximize the signal level V<sub>L</sub> by using a voltage source whose output impedance Z<sub>S</sub> is as small as possible and by using a receiving device whose input impedance Z<sub>L</sub> is as large as possible. When <math>
Z_L \gg Z_S
</math> (typically by at least ten times), this is called a bridging connection and has a number of effects including:
- Advantages:
- Reduces the 6dB attenuation incurred by impedance matching, which helps by reducing the amount of make-up amplification required and by maintaining a high signal-to-noise ratio.