Traditional Op-Amp and new VCII: A comparison on analog circuits applications

Although the idea of second generation voltage conveyor (VCII) dates back to two decades ago, only in a recent publication by authors, its applications and capabilities were studied. Considering that VCII-based circuits are also realizable by Operational Amplifiers (Op-Amps), in this paper a comparison between circuits implementable using either Op-Amp or VCII is drawn. The transfer function and main characteristics of each implementation are given. To validate the presented theory Spice simulations performed in 0.18 µm CMOS technology with a supply voltage of ±0.9 V are provided. The achieved results show that the circuits based on Op-Amp require a very high gain for this active block, to be traded off with bandwidth. As a consequence, Op-Amp can be successfully replaced by VCII for high frequency applications. In addition, the output of Op-Amp based circuits is of inverting (or non-inverting) type while both inverting and non-inverting outputs are achievable in the VCII based circuits. Other benefits are achieved: more importantly, using VCII to implement non-inverting voltage summing circuit is an effective solution to remove the undesired cross-talk effect that occurs in Op-Amp based one. PSpice simulations complete the comparison.