Abstract

The current-feedback OTA (CFB OTA) recently appeared in a new classification of operational amplifiers. It is dual to the operational floating amplifier (OFA), so all OFA circuits can readily be transposed into CFB OTA circuits. This paper discusses the theoretical basis of the CFB OTA, shows its relation to the OFA, and compares their performance in a simple V--I converter by showing how both can be built with the same two transistor stages. The advantages and disadvantages of the CFB-OTA implementation are discussed as well, but the main advantage of introducing the CFB OTA is that its introduction is virtually for free: most current opamps from the literature can be converted into CFB OTAs by re-wiring their input stage, without adding or re-sizing a single transistor.

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