fT integrator-a new class of tuneable low-distortion instantaneous companding integrators for very high-frequency applications

A novel design methodology for realizing tuneable very high-frequency low-distortion integrators is presented, which we call the f_T integration. The technique, which is a special ease of the companding technique, not only achieves integrator linearization but also offers similar advantages to the distributed CMOS transistor-only filtering technique in terms of chip area and very high-frequency operation. The operating principle of the f_T integrator is both explained via a circuit model and a dynamic charge control model in which the physical mechanism underlying the f_T-integration technique is revealed. Detailed analysis of performance degradation due to nonideal effects as well as some design considerations are discussed and means for improvement are proposed. A fully balanced f_T integrator with frequency tuneability and adjustable DC gain is then developed. Promising results, particularly in terms of tuneability, linearity, and high-frequency performance, were obtained from both preliminary experimental results using a circuit prototype and simulations using HSPICE, confirming the viability of the technique for high-frequency and high-performance filter applications