A CMOS continuous-time current-mode filter technique

A CMOS continuous-time current mode filtering technique is described. A differential current-mode integrator was designed, fabricated, and used in a leapfrog configuration to realize lowpass ladder filters. A fifth-order lowpass filter with a -3-dB cutoff frequency of 40 MHz was achieved with a power dissipation of 28 mW in a 2- mu m n-well CMOS technology. The filter cutoff frequency was tuned by simply changing the bias current to the filter. A third-order elliptic lowpass filter was also integrated to verify the implementation of transmission zeros. Measured and simulated results agreed closely, and the active filter area was only 0.056 mm/sup 2//pole.<>