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Active filter
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<p>An active filter is a type of <a href="/facts/Analog_circuit/Bnlnfwwv">analog circuit</a> implementing an <a href="/facts/Electronic_filter/ny7k6VxV">electronic filter</a> using active components, typically an <a href="/facts/Amplifier/pnRgxncC">amplifier</a>. Amplifiers included in a filter design can be used to improve the cost, performance and predictability of a filter. </p><p>An amplifier prevents the load impedance of the following stage from affecting the characteristics of the filter. An active filter can have complex poles and zeros without using a bulky or expensive inductor. The shape of the response, the Q (<a href="/facts/Quality_factor/NNjGLb5b">quality factor</a>), and the tuned frequency can often be set with inexpensive variable resistors. In some active filter circuits, one parameter can be adjusted without affecting the others. </p>