Digital frequency tuning technique based on current division for integrated active RC filters

A novel digital frequency tuning technique is presented for integrated active RC filters. Instead of varying the values of the capacitors or resistors as in traditional approaches, the proposed technique achieves frequency tuning by dividing the currents that flow from resistors to virtual grounds. Current division is performed through a digitally programmable current division network added at each virtual ground. The technique features compact size, wide tuning range and high linearity. Transistor level simulation results are presented to demonstrate the technique.