A programmable coefficient continuous-time A/D Δ-Σ modulator

A continuous-time Δ-Σmodulator has been proposed that uses floating-gate transistors to program the feed-forward and feedback coefficients. The G_m-C integrators are designed to run in subthreshold and take advantage of the floating gate circuit architecture to increase the linear range and minimize V_TH error. A 2nd order modulator was fabricated in 0.5μm CMOS with measured maximum SNR of 59.2dB, maximum SINAD of 50.27 and a DR approximately 50dB. A modulator with an unlatched comparator was also tested and an initial investigation has begun into the asynchronous behaviour of the modulator when it is without clocking.