Current-Mode Universal Biquad Using Current Followers: A Minimal Realization

Abstract

A new universal biquad filter is presented which employs a minimum number of active elements (only three current followers (CF)) along with a minimum number of passive components (i.e. only two resistors and two capacitors). The new circuit provides all the five standard filter responses (namely lowpass, bandpass, highpass, notch and allpass) from the same structure without requiring any component matching conditions and with explicit current outputs available from high output impedance terminals. The workability of the proposed universal biquad, realised with unity-gain current followers implemented in 0.35 µm CMOS and operated from 1.65 volts DC power supplies, is established by SPICE simulations.

Keywords

• Universal filters
• current followers
• current-mode circuits