measuring off state capacitance

[hakeen]

off state capacitance

Hello

I have a SSR (aka PhotoMOSFET). The inner structure is shown below. it is 60V, up to 1A at MOSFET side.

How can I measure the off-state capacitance of the MOSETs of the component?

Thanks for any help.

Regards
Hakeen

 

[eem2am]

1. turn it off
2. measure the capacitance.

..as follows.....

i = cdv/dt

shove a resistor in series with the terminals 3 and 4

shove a square wave across this RC combbo.

Take a look at the voltage across the terminals 3 to 4. Use Laplace to get the capacitance.

or just use 5RC = time to aiming voltage

im sure you can work the rest out from here.

you must see i = cdv/dt

you know i(t) = v(t)/R
v(t) = v across res


In fact.
i(t) = V/R * (1-e(-Rt/L))