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For example, an amplifier with 100,000 ohm input impedance looks equivalent to a 100,000 ohm resistor to the signal coming into it. IN AUDIO SYSTEMS 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 In general, this configuration will be more resistant to noise (particularly power line Hum ). The best circuits are created by using a Voltage Follower in the source with the pull-up (load) resistor at the signal receiver. IN VIDEO AND HIGH FREQUENCY SIGNAL SYSTEMS In video and other systems the impedance of inputs, Transmission Line s, and outputs are designed to be the same. This is known as ''reflectionless Impedance Matching '' or a ''matched connection''. In this case, the impedances must be matched in order to prevent reflected waves from the signal receiver. In video circuits these reflections can cause "ghosting", where the time-delayed echo of the principle image appears as a weak and displaced image (typically to the right of the principle image). Z IN RADIO FREQUENCY POWER SYSTEMS In Circuits carrying high Power it is important that the impedances be matched for several reasons.
In the case of purely resistive impedances (no reactive components), the two types of impedance matching are identical. SEE ALSO EXTERNAL LINKS |
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