Active Filter vs Passive Filter
过滤器是一类用于信号处理的电子电路,以允许或阻止所需的信号范围或信号。可以根据属性(例如被动,模拟 - 数字,线性 - 非线性,离散时间 - 连续时间,时间不变 - 时间变体和无限脉冲响应 - 有限的脉冲响应)对过滤器进行多个级别分类。
Active and passive filters are differentiated by the passivity of the components used in the filter circuit. If a component consumes power or incapable of power gain then it is known as a passive component. Components that are not passive are known as active components.
More about Passive Filters
Resistors, capacitors, and inductors all consume power when a current passes through them, and incapable of power gain; therefore, any RLC filter is a passive filter, especially with the inductors included. Another major characteristic of the passive filters is that the filters do not need an external power source for operation. The input impedance is low and the output impedance is high, allowing self-regulation of the voltages driving the loads.
Usually, in passive filters, load resistor is not isolated from the rest of the network; therefore, change in the load may affect the characteristics of the circuit and filtering process. However, there are no bandwidth restrictions for the passive filters, allowing satisfactory operation at very high frequencies. In lower frequency filters, the inductor used in the circuit tends to be larger, making the circuit bulkier. If higher quality and smaller size are required, the cost is increased significantly. Passive filters also create a little amount of noise, due to the thermal noise in the elements. Nevertheless, with proper design this noise amplitude can be minimized.
由于没有信号增益,因此必须在以后进行信号扩增。有时可能需要缓冲液放大器来补偿输出电路的差异。。
More about Active Filters
Filters with components such as operational amplifiers, transistors, or other active elements are known as active filters. They use capacitors and resistors, but inductors are not used. Active filters require an external power source to operate because of the power consuming active elements in the design.
Since no inductors are used, the circuit is more compact and less heavy. Its input impedance is high and the output impedance is low, allowing to drive low impedance loads at the output. Generally, the load is isolated from the internal circuit; hence variation of the load does not affect the characteristics of the filter.
The output signal has a power gain, and the parameters like gain pass band and cutoff frequency can be adjusted. Several drawbacks are inherent to the active filters. The changes in the power supply may cause changes in the output signal magnitude and the high frequency ranges are limited by the active element properties. Also, feedback loops used for regulating the active components may contribute to oscillation and noise.
What is the difference between Active and Passive Filters?
• Passive filters consume the energy of the signal, but no power gain is available; while active filters have a power gain.
•主动过滤器需要外部电源,而被动过滤器仅在信号输入上运行。
• Only passive filters use inductors.
• Only active filters use elements kike op-amps and transistors, which are active elements.
• Theoretically, passive filters have no frequency limitations while, active filters have limitations due to active elements.
• Passive filters have a better stability and can withstand large currents.
• Passive filters are relatively cheaper than active filters.
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