[SOLVED] How to find minimum value of decoupling capacitor (in the below question) ?

[OmerN]

[solved] How to find minimum value of decoupling capacitor (in the below question) ?

I attached a question about how to find minimum value of decoupling capacitor. I dont have any idea yet. Please help..


**broken link removed**

 

[crutschow]

C1 is initially charged to 3.3V. M2 suddenly connects the 3pF load (which has been discharged by M1) in parallel with C1.

One way to solve the problem is to determine what value of C1 will cause the amount of charge on C1 to be reduced by a factor of .15/3.3 when the amount of charge required by the 3pF load is removed from C1 due to the parallel connection (which charges the 3pF to (3.3V - .15V).

 

[chuckey]

Looks like C1/ 3 = 3.3/.15 ~ 66 pF
Frank

 

[Borber]

Q=C*3.3=(C+3)*(3.3-.15)
C*3.3=(C+3)*(3.3-.15)
C=3*3.15/.15=63
C1=63pF

 

[crutschow]

You guys are doing the homework for him and spoiling all the fun. :wink:

 

[OmerN]

thanks guys, that was so helpful