Bandpass modulators combine over-sampling and noise shaping to get very high resolution in a narrowband. In recent years interests have been seen in wireless system and software radio using the modulators to digitize signals near the front end of radio receivers. Such applications necessitate clocking the modulators at a high frequency (MHz or above). Therefore a loop filter is required in continuous-time circuits (e.g., using transconductors and integrators) rather than discrete-time circuits (e.g., using switching capacitors) where the maximum clocking rate is limited by the bandwidth of...