Abstract

A CMOS transconductor is a functional block which can transfer voltage signals to current signals. Thus, it is a commonly used interface between the physical world and the current signal processing systems. In order not to affect the performances of the main current signal processing system, high-performance transconductor structures need to be designed. The major concerns of modern analog systems include lower power dissipation and wider bandwidth in addition to the application related performances, such as, high gain, high linearity and so on. Unlike most researches that have been conducted on improving the single performance of a transconductor structure, a systematic methodology which targets on the performance-power ratio of CMOS transconductors is proposed in this work. The objective function defined for optimizing the performance-power ratio is a transconductor's frequency versus power ratio. The significance of the frequency-power ratio is that it represents how much bandwidth a structure can achieve while consuming unit DC power. A transconductor structure with maximal frequency-power ratio provides wider bandwidth than the structure with non-maximal frequency-power ratio when both consume the same DC power; or on the other hand, the structure with maximal frequency-power ratio consumes less DC power than the non-maximized structure when both operate at the same bandwidth. Theoretical derivations, numerical calculations as well as HSPICE simulations on various transconductor structures are conducted to prove the effectiveness of the proposed optimization methodology. Two test chips are also fabricated and measured to verify the analyses. A few transconductor-based analog systems are studied to illustrate the impact of the transconductor optimization on the system. Other important design issues, such as, environmental variations, are also discussed in the work