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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 signal is neither driven to a logical high nor low level; this third condition leads to the description "tri-stated". [1] Such a signal can be seen as an open circuit (or "floating" wire) because connecting it to a low impedance circuit will not affect that circuit; it will instead itself be pulled to the same voltage as the actively driven ...
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.
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 ...
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.
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 ...
Equivalent unbalanced and balanced networks. The impedance of the series elements in the balanced version is half the corresponding impedance of the unbalanced version. Fig. 3. To be balanced, a network must have the same impedance in each "leg" of the circuit. A 3-terminal network can also be used as a 2-port.
The resultant circuit is nothing other than a resonant LC circuit in which the energy continues to oscillate to and fro. This oscillation is called reactive power . Power factor correction (where an inductive reactance is used to "balance out" a capacitive one), is essentially the same idea as complex conjugate impedance matching although it is ...