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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.
For a voltage source the return ratio is minus the ratio of the voltage across the dependent source divided by the voltage of the independent replacement source. For a current source, short-circuit the broken leads of the dependent source. The return ratio is minus the ratio of the resulting short-circuit current to the current of the ...
Figure 2: Small-signal circuit for finding output resistance of the Widlar source shown in Figure 1. A test current I x is applied at the output, and the output resistance is then R O = V x / I x. An important property of a current source is its small signal incremental output impedance, which should ideally be infinite.
Some electronics simulators integrate a schematic editor, a simulation engine, and an on-screen waveform display (see Figure 1), allowing designers to rapidly modify a simulated circuit and see what effect the changes have on the output. They also typically contain extensive model and device libraries.
A circuit is a current source only to the extent that its output current is independent of its output voltage. In the circuits of Fig. 1 and Fig. 2, the output voltage of importance is the potential from the collector of Q 3 to ground. The measure of that independence is the output impedance of the circuit, the ratio of a change in output ...
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 characteristic impedance or surge impedance (usually written Z 0) of a uniform transmission line is the ratio of the amplitudes of voltage and current of a single wave propagating along the line; that is, a wave travelling in one direction in the absence of reflections in the other direction. Alternatively and equivalently it can be defined ...
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.