Single Amplifier Bi-Quadratic Filter Topologies in Transimpedance Configuration

Active-RC configurations, implemented as cascaded bi-quadratic sections (biquads), are the filters of choice for low distortion applications in the base-band. For low power and area applications, single amplifier biquads are best, and are well studied in literature. However, in many applications the input signal is in current domain while the output is a voltage. Output of a current steering digital-analog converter, and output of a down-conversion mixer, are two such examples. In this paper, the authors propose two generic classes of single amplifier bi-quadratic low-pass filter topologies, achieving a second order roll-off in transimpedance (-to-) configuration. Both these topologies are derived with the constraint of fully differential signal processing. The transimpedance active-RC configurations presented here eliminate redundant current-voltage-current conversion and hence provide immense advantages in terms of noise and linearity.