Systematic design of companding systems by component substitution

A design method for externally linear, internally nonlinear systems is pres ented which allows them to be derived from externally equivalent systems in a systematic way and with a minimum synthesis effort, just performing a si mple component-to-component substitution. As a particular case, the synthes is of the most popular versions of voltage companding systems from external ly equivalent Gm-C systems is addressed. The practical design of companding systems based on the MOS square law (Square-Root Domain systems) is fully illustrated along the complete design flow, from the Gm-C prototype to sili con. These systems, feasible in CMOS technologies and formerly difficult to obtain due to the inherent complexity of existing synthesis methods, parti cularly benefit from the simplicity of the proposed approach. Experimental results for two versions of tunable Square-Root Domain biquadratic filters and oscillators thus obtained and fabricated in a 2.4-mum CMOS process are presented, featuring favorable tunability and low THD.