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In electrical engineering, impedance is the opposition to alternating current presented by the combined effect of resistance and reactance in a circuit. [1]Quantitatively, the impedance of a two-terminal circuit element is the ratio of the complex representation of the sinusoidal voltage between its terminals, to the complex representation of the current flowing through it. [2]
The input impedance of an infinite line is equal to the characteristic impedance since the transmitted wave is never reflected back from the end. Equivalently: The characteristic impedance of a line is that impedance which, when terminating an arbitrary length of line at its output, produces an input impedance of equal value. This is so because ...
Z-parameters are also known as open-circuit impedance parameters as they are calculated under open circuit conditions. i.e., I x =0, where x=1,2 refer to input and output currents flowing through the ports (of a two-port network in this case) respectively.
To minimize reflections, the characteristic impedance of the transmission line and the impedance of the load circuit have to be equal (or "matched"). If the impedance matches, the connection is known as a matched connection, and the process of correcting an impedance mismatch is called impedance matching. Since the characteristic impedance for ...
In analog circuits a high impedance node is one that does not have any low impedance paths to any other nodes in the frequency range being considered.Since the terms low and high depend on context to some extent, it is possible in principle for some high impedance nodes to be described as low impedance in one context, and high impedance in another; so the node (perhaps a signal source or ...
It uses the principle that the positive phase angle of an inductive impedance can be compensated by the negative phase angle of a capacitive impedance when put in the opposite arm and the circuit is at resonance; i.e., no potential difference across the detector (an AC voltmeter or ammeter)) and hence no current flowing through it. The unknown ...
The actual output impedance for most devices is not the same as the rated output impedance. A power amplifier may have a rated impedance of 8 ohms, but the actual output impedance will vary depending on circuit conditions. The rated output impedance is the impedance into which the amplifier can deliver its maximum amount of power without failing.
This is different from what is normally meant by a symmetrical circuit, which is a circuit showing symmetry of its components about a vertical line at its midpoint. An example of a symmetrical circuit is shown in figure 2. Circuits designed for use with balanced lines will often be designed to be both balanced and symmetrical as shown in figure 4.