Programmable time-multiplexed switched-capacitor variable equalizer for arbitrary frequency response realizations

A time-multiplexed digitally-programmable switched-capacitor (SC) variable equalizer which allows the realization of arbitrary frequency responses is presented. The circuit performs the same operation as a cascade of N second-order programmable equalizers, where N is also the multiplexing order. Except the storing capacitors, the rest of the circuitry is shared for all individual equalizer functions (channels), resulting in silicon area savings higher than 60% with respect to a direct circuit implementation for N=4. The impact on circuit performance of crosstalk effects is discussed. Experimental results of a 3-V timesharing SC equalizer architecture fabricated in a CMOS 1.2 μm technology are given for different values of the multiplexing order. The circuit has been designed to be incorporated in a programmable hearing aid device