Lazarus
New Member
Offline
Posts: 2
|
Aaron,
OK, I had assumed you were bottom-plate sampling.
Here are several things you will need to check:
1 - If you decrease the sample rate (for the same input frequency), does the performance improve? If it does, then this tells you that the bootstrap circuit is taking time to charge up (and cutting down the track time). 2 - If you decrease the input frequency for the same sample frequency, does the performance improve? If it does, then one possible reason is the phase delay of the bootstrapped signal at the gate as compared to the source / drain. 3 - How much does the bootstrapped voltage drop when the TH goes from hold to track (due to the parasitic caps)?
Finally, note that the on resistance is inversely proportional to VGS-VT. Bootstrapping holds VGS constant. VT is still nonlinear. If you can control the body in your process, then you will need to make VSB = 0 during track mode.
By the way, dummy transistors won't work for the linearity you are targeting.
-- L
|