rdfs:comment
| - A passive filter is a kind of electronic filter that is made only from passive elements -- in contrast to an active filter, it does not require an external power source (beyond the signal). Since most filters are linear, in most cases, passive filters are composed of just the four basic linear elements -- resistors, capacitors, inductors, and transformers. More complex passive filters may involve nonlinear elements, or more complex linear elements, such as transmission lines. Television signal splitter consisting of a passive hi-pass filter (left) and a passive low-pass filter (right). The antenna is connected to the screw terminals to the left of center.
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abstract
| - A passive filter is a kind of electronic filter that is made only from passive elements -- in contrast to an active filter, it does not require an external power source (beyond the signal). Since most filters are linear, in most cases, passive filters are composed of just the four basic linear elements -- resistors, capacitors, inductors, and transformers. More complex passive filters may involve nonlinear elements, or more complex linear elements, such as transmission lines. Television signal splitter consisting of a passive hi-pass filter (left) and a passive low-pass filter (right). The antenna is connected to the screw terminals to the left of center. A passive filter has several advantages over an active filter:
* Guaranteed stability
* Passive filters scale better to large signals (tens of amperes, hundreds of volts), where active devices are often impractical
* No power consumption, but the desired signal is invariably attenuated. If no resistors are used, the amount of signal loss is directly related to the quality (and the price) of the components used.
* Inexpensive (unless large coils are required)
* For linear filters, generally, more linear than filters including active (and therefore non-linear) elements They are commonly used in speaker crossover design (due to the moderately large voltages and currents, and the lack of easy access to power), filters in power distribution networks (due to the large voltages and currents), power supply bypassing (due to low cost, and in some cases, power requirements), as well as a variety of discrete and home brew circuits (for low-cost and simplicity). Passive filters are uncommon in monolithic integrated circuit design, where active devices are inexpensive compared to resistors and capacitors, and inductors are prohibitively expensive. Passive filters are still found, however, in hybrid integrated circuits. Indeed, it may be the desire to incorporate a passive filter that leads the designer to use the hybrid format.
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