abonic
Junior Member level 2
Dear guys,
Due to the periodic drift of the output CM level, the outputs (Voutp & Voutn) of a fully differential amplifier accordingly drift even with sufficient SR and UGB, as shown in the figure attached. This is the typical case.
However, if we look at the differential signal (Voutp-Voutn), the influence of the CMFB vanishes. The differential signal seems perfect.
Comparing the single-end signals and the differential representation, we may conclude that the former are not well settled, whilst the latter is well settled. (Confusion??)
Actually, in my practise, opamp exhibiting this phenomenon still works well preliminarily by simulation (this conclusion has to be fully verified further) , however, I'm pretty worrying about the result of the final testing.
My question is, when we talk about the settling of a fully-differential amplifier, which one we mean, signal-end signals with effect of CMFB or the differential signal, providing that the drift of the output CM level is not severe.
Thank you!
Due to the periodic drift of the output CM level, the outputs (Voutp & Voutn) of a fully differential amplifier accordingly drift even with sufficient SR and UGB, as shown in the figure attached. This is the typical case.
However, if we look at the differential signal (Voutp-Voutn), the influence of the CMFB vanishes. The differential signal seems perfect.
Comparing the single-end signals and the differential representation, we may conclude that the former are not well settled, whilst the latter is well settled. (Confusion??)
Actually, in my practise, opamp exhibiting this phenomenon still works well preliminarily by simulation (this conclusion has to be fully verified further) , however, I'm pretty worrying about the result of the final testing.
My question is, when we talk about the settling of a fully-differential amplifier, which one we mean, signal-end signals with effect of CMFB or the differential signal, providing that the drift of the output CM level is not severe.
Thank you!