How to measure capacitance without letting the voltage become larger than 0V?

[demodb]

Hi guys, anyone has any idea how to measure a capacitance without letting the voltage over the capacitance becomes larger than 0V. Needs to know the parasitic capacitance on a port which can not become larger than 0V (design constraint).

 

[Sal]

measure capacitance

Hi

No larger than 0V means that the voltage can be negative? or no voltage at all?

Sal

 

[demodb]

Re: measure capacitance

yes, it means the voltage on the pin needs to be within -30V and 0V.

 

[yjkwon57]

Re: measure capacitance

You will use a small-signal sine-wave generator of a fixed peak-to-peak voltage and a specified frequency. Then, you will measure the current flowing through the capacitor, which is also a sinusoidal in waveform. And, you will calculate C using the equation i = jwc * v, where j means a phase shift of pi / 2.

 

[demodb]

Re: measure capacitance

thx, i thought of that last night. I apply that sine wave with a negative DC voltage.