Limits to the dynamic range of low-power continuous-time integrators

The power consumption of active filters limits the achievable dynamic range. In this paper, we start by considering ideal electronic building blocks, and we derive the fundamental limits to the dynamic range of different topologies of continuous-time integrators, for a given power consumption. Then, by using simplified nonideal circuit models, we present design guidelines for the optimization of the dynamic range to power consumption ratio of the integrators. We, thus, obtain practical limits to the dynamic range, as functions of the transition frequency of the transistors. We demonstrate the possibility of approaching these limits by designing a practical CMOS circuit: an 8 MHz second-order bandpass filter with Miller integrators. The performance of the filter was evaluated by HSPICE simulations, using full device models; the resulting dynamic range to power consumption ratio is close to the theoretical limits