Universal Switched-Current Integrator Blocks for SI Filter Design

The switched-current (SI) circuit is a circuit technique which is able to realize analog sampled-data circuits with a standard CMOS technology. Among all the basic SI circuits, the memory cell circuit is the most primitive element. In this work, a practical SI memory cell which employs negative feedback circuitry and glitch reduction technique is first presented. Based on this basic cell, a universal SI integrator is then developed. General first and second order building blocks are subsequently developed for the cascade design of SI filters. These general building blocks can be used to generate all types of first and second order filters. To verify the accuracy of the SI circuits, test filters including a first order low-pass filter, a second order Chebyshev low-pass filter, and a fifth order Chebyshev low-pass filters have been designed and verified with HSPICE. The simulation results of the frequency response characteristics show good agreement with the theoretical results.