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Design >> Mixed-Signal Design >> How to store the difference of 2 voltages on capacitor
https://designers-guide.org/forum/YaBB.pl?num=1527499599

Message started by josvlsi on May 28^th, 2018, 2:26am

Title: How to store the difference of 2 voltages on capacitor
Post by josvlsi on May 28^th, 2018, 2:26am

Suppose we have two voltages V1 and V2 how can we store the voltage V1-V2 on a given capacitor?
I tried charging the top plate of the capacitor to V1 and then charged the bottom plate of the capacitor to V2. but the value of the voltage across the capacitor is not V1-V2, how can we do this?
I am trying to simulate this in Cadence.

Title: Re: How to store the difference of 2 voltages on capacitor
Post by subtr on Aug 13^th, 2019, 12:07pm

Did you disconnect the capacitor and make it floating at any point of time? If you read how SAR ADC's work.
1. charge a cap by connecting V1 in parallel to it.
2. disconnect the cap's bottom plate from the ground. The cap still is charged to V1 and it's bottom plate is at Ground because it's V1 - Vcap.
3. Now you can disconnect your input source and Connect V2. Your output is V2 - Vcap or V2 - V1.