Vast attention has been paid to active filters over the years. As cheap integrated OpAmp replaced its discrete counterpart, it became feasible to consider active-RC filters. Similarly the development of integrated transconductance led to new filter configurations using only active devices and capacitors. The continuing increase in the operating frequencies of modern systems led to the emerging of active LC filters. Several novel circuit building blocks are introduced. A pseudo-differential fully balanced CMOS OTA architecture with inherent CM detection is proposed. On the level of system architectures, a low-voltage 4th order RF bandpass filter structure based on emulation of two magnetically coupled resonators is presented. As part of a direct conversion 802.11b/Bluetooth receiver, a dual mode 2.5V BiCMOS 5th order channel selection filter is designed. As part of a Bluetooth transmitter, a low-power quadrature DDFS based on piecewise linear approximation is introduced. This bookis concentrating on the design issues of high performance continuous-time integrated filters, and should be especially useful to professionals in the field of CMOS analog & mixed signal circuit design.