fully differential switched capacitor amplifier

[namel]

hi,
Can anyone please clarify-
1. I have read somewhere that while in the holding mode, the input common mode voltage of the differential amplifier is equals to output common mode. Does that necessitates the vcmin range should include vcmout? If not what will happen?
2. what should be the input voltage swing range, should it be the same?

 

[erikl]

1. I have read somewhere that while in the holding mode, the input common mode voltage of the differential amplifier is equals to output common mode. Does that necessitates the vcmin range should include vcmout? If not what will happen?

During hold mode the amplifier is active. In this state the value of the output common mode voltage first and foremost has not much to do with the input common mode voltage, but essentially depends on the amplifier circuit itself and its feedback configuration.

For a well designed amplifier, the output (common mode) voltage range is nearly rail-to-rail (minus saturation voltages), s. this AD tutorial. The input common mode range usually is (much) smaller, so it can never include vcmout, i.e. this is not necessary.

2. what should be the input voltage swing range, should it be the same?

Same as what? The input voltage swing range should be confined within the input common mode voltage range, whereas the max. differential input voltage swing is defined by the output voltage range divided by the gain.