High Speed Active Filters

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Filters built from resistors (R), inductors (L) and capacitors (C) are known as RLC or passive filters and are the dominant type of filter for high frequency applications.The performance of these filters is typically limited by the inductors which are large, expensive and far from ideal in an electrical sense. By using amplifiers and feedback,the same filter characteristics can be achieved without the use of inductors, these filters are known as “active  filters”. An active filter will perform well only to the
extent that the amplifiers in it behave in an ideal sense, so traditionally active filters have been limited to applications at frequencies below 1MHZ. With the advent of low cost, very high speed operational amplifiers,it is now feasible to realize active filters with frequency ranges in the tens of MHZ. With some of the newer high speed amplifiers such as the CLC449 – a 1.2GHz
bandwidth amplifier, filters with corner frequencies above 100MHz have been built.
由电阻(R)、电感(L)和电容(C)构建的滤波器被称为RLC或无源滤波器，是高频应用的主要滤波器类型。这些滤波器的性能通常受到电感器的限制，电感器体积大，价格昂贵，在电气意义上远非理想。通过使用放大器和反馈，可以在不使用电感器的情况下实现相同的滤波器特性，这些滤波器被称为“有源滤波器”。有源滤波器只有在其放大器表现理想的情况下才会表现良好，因此传统有源滤波器的应用仅限于1MHZ以下的频率。随着低成本、超高速运算放大器的出现，实现频率范围在几十兆赫兹的有源滤波器已成为可能。随着一些较新的高速放大器，如CLC449 -一个1.2GHz带宽放大器，角频率超过100MHz的滤波器已经建立。