- What is the purpose of connecting capacitors to the gates in this bucket brigade device circuit? Why aren't they just connected to ground?
- In every 2nd place there is a buffer transistor. How do these transistors prevent the voltage loss of the previous capacitors?
It isn't so much that the capacitors are connected to the gates per se, but that they're connected to the clock signals.
The point is, the charge will flow from one capacitor to another only if the voltage on the first capacitor is higher. Only by raising the "bottom" of a capacitor to the highest system voltage during the high phase of its clock can you be sure of transferring all of its charge to the next capacitor.
The "buffer" transistors (the ones whose gates are connected to VGG) are actually there to make sure that charge transfers only in the forward direction, and that the capacitors never take on a negative voltage. Otherwise, the buckets would lose charge in both directions, and all you'd get out at the far end would be an average voltage for the whole chain.