Analysis of the Effect of Transit Capacitances in Fully Differential Operational Transconductance Amplifiers

I. Uzunov (GlobalFoundries, Bulgaria), B. Nikov (On Semiconductor, Switzerland)

The paper considers the analysis of influence the transit capacitances, connecting input and output nodes in fully differential (FD) operational transconductance amplifiers (OTA) and having effect basically in single-stage OTAs. First is shown the incompleteness of the often used approach of representing of these capacitances by a positive zero of OTA transconductance. Then are proposed single-ended equivalent circuits for both cases when FD OTA is used as inverting and non-inverting amplifier. They simplify the analysis, which is demonstrated by considering of two examples: single OTA with different loads and the gyrator resonance circuit.