Performance comparison of high-order IFLF and cascade analogue integrated lowpass filters

The magnitude and delay performance of integrated continuous-time gm–C lowpass filters is discussed. The analysis is based on tenth-order filters with equiripple group delay, implemented in CMOS fully differential form as inverse-follow-the-leader feedback (IFLF) and cascade topologies. A very-high-frequency operational transconductance amplifier (OTA) is used as the basic building block. The sensitivity performance is assessed by simulating IFLF and cascade filters with 27 real CMOS models released from MOSIS. Experimental and simulation results show that the passband magnitude sensitivity of the cascade filter is larger than that of the IFLF filter. In the stopband, the opposite is true. The results demonstrate that the group delay performance, on the other hand, is worse in the IFLF filter than in the cascade filter.