Measure Cgd Cgs Cds using MOSFET

Alec_t

Joined Sep 17, 2013
14,201
Welcome to AAC!
Why do you want to measure Cgs? The value (5.2n for the FET shown) is specified in the model.
 

Thread Starter

CtyNatty

Joined Sep 10, 2017
12
Welcome to AAC!
Why do you want to measure Cgs? The value (5.2n for the FET shown) is specified in the model.
Hi, how do you get that ?
Actually i need to get all that so that i can calculate input capacitance and so on.
To compare with the datasheet. I use the formula stated on my .asc
I'm not sure whether that circuit is the right configuration to measure parasitic capacitance.
 

Thread Starter

CtyNatty

Joined Sep 10, 2017
12
Right-click on the FET symbol, left-click on "Pick New MOSFET", read the .model text to the right of the device name.

Many (most/all?) Spice models are based on the device datasheets, so simulation would yield the datasheet values. You'd be going round in circles.
How about this one ? I use the spice lib from renesas. I create new symbol etc and need to run simulation to compare with the datasheet.
Does it also the same case ? I use plot .step'ed .meas data function to plot the graph. But not sure on how to read the information.
 

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Thread Starter

CtyNatty

Joined Sep 10, 2017
12
Btw, do you know how to use .meas statement to find the value of capacitance at Vce=25V ?
I try to use this equation but failed to measure it.

.meas Cies FIND V(cies) WHEN V(Vce)=25

Is it because it mixed up between AC and DC ?
Before this it worked just fine for other measurements.
 

Thread Starter

CtyNatty

Joined Sep 10, 2017
12
Btw, do you know how to use .meas statement to find the value of capacitance at Vce=25V ?
I try to use this equation but failed to measure it.

.meas Cies FIND V(cies) WHEN V(Vce)=25

Is it because it mixed up between AC and DC ?
Before this it worked just fine for other measurements
 
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