The Designer's Guide Community Forum

The Designer's Guide Community Forum
https://designers-guide.org/forum/YaBB.pl
Design >> Analog Design >> How to distinguish charge injection and clock feedthrough?
https://designers-guide.org/forum/YaBB.pl?num=1374402302

Message started by Yutao Liu on Jul 21^st, 2013, 3:24am

Title: How to distinguish charge injection and clock feedthrough?
Post by Yutao Liu on Jul 21^st, 2013, 3:24am

Hello everyone,
I wanna know how to distinguish charge injection and clock feed-through with simulation, because both have impact on output accuracy of SC.
As mentioned in Razavi's book, charge injection happens when switch alters from "on" to "off". And clock feed-through comes out every clock transition. So can we use this difference as criteria?

Thanks a lot.
Yutao Liu

Title: Re: How to distinguish charge injection and clock feedthrough?
Post by loose-electron on Aug 2^nd, 2013, 7:05pm

Yutao Liu wrote on Jul 21^st, 2013, 3:24am:

Unfortunate, but the transistor model capacitive distribution in many models is not well done and trying to get something quantitative there is often a little meaningless.

However, in my opinion the difference comes down to this:

Clock feedthrough is the capacitive coupling from the gate control input to the output of a switch.

Charge injection is the dumping of the charge stored in the channel used to invert the channel of the MOS device.

In theory, the magnitude of one should be fixed, for the same amount of channel inversion. (namely the charge injection)

The other ones (clock feedthrough) should be variable dependent upon the clock magnitude and dv/dt of the clock signal rise-fall.