Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Register Log in

Power MOSFET Ciss, Coss, Crss test conditon understanding.

Status
Not open for further replies.
P

parachutes30

Junior Member level 1
Junior Member level 1
Joined
Nov 8, 2016
Messages
19
Helped
2
Reputation
4
Reaction score
2
Trophy points
3
Activity points
154
test condition such as: VGS = 0 V, f = 1 MHz, VDS = 25V

what does Vgs=0V mean? is it short - circuit or open - circuit of G and S?
 

Hi,

"Floating" means the voltage is not defined.

V_gs = 0V definitely means G and S are short.

Klaus
 

The specification tells the measurement DC bias conditions.

To measure Ciss or Crss, you'll hardly short gate and source.
 

Hi

True. I was too fast with my answer. I just read "open" and "short" .... and "open" was not true.
I didn't consider a third mode.

Klaus
 

FvM said:
The specification tells the measurement DC bias conditions.

To measure Ciss or Crss, you'll hardly short gate and source.
Click to expand...

Ciss is the capacitance Cgs + Cgd, and I want to test it by my LCR meter.
So how can I do it? should I short-circuit D and S ? if i do this, obviusly I am short-circuiting the 15V power supply dc bias.
 

Hi,

V_gs = 0V.....and as FvM correctly stated this is the DC operation point.
--> use a high ohmic resistor across G and S to ensure 0V DC.

But you want to test input capacitance:
--> connect a high quality foil capacitor from your ESR measurement device to G of the mosfet.
The capacitance need to be way higher than the exoected DUT capacitance to avoid influence in the measurement result.
If you take a 100 times higher capacitor...you should be safe.

Note: the AC voltage should be small enough to be below V_gs_th.

Klaus
 

KlausST said:
Hi,

V_gs = 0V.....and as FvM correctly stated this is the DC operation point.
--> use a high ohmic resistor across G and S to ensure 0V DC.

But you want to test input capacitance:
--> connect a high quality foil capacitor from your ESR measurement device to G of the mosfet.
The capacitance need to be way higher than the exoected DUT capacitance to avoid influence in the measurement result.
If you take a 100 times higher capacitor...you should be safe.

Note: the AC voltage should be small enough to be below V_gs_th.

Klaus
Click to expand...

so when I test Ciss , i short the D and S and the real test condition is : VGS = 0 V, f = 1 MHz,
and when I test Coss, I short the G and S and the real test condition is : VDS = 25V, f = 1 MHz,
 

After I contact with the support of a manufacturer. what i know is:
When test Ciss, LCR meter is across the G and S, Vds = 15V, and there is a big cap between the D and S to AC-short the D and S.
When test Coss, LCR meter is across the D and S, Vds = 15V, and G and S is really shorted.
 
  • Like
Reactions: FvM

    FvM

    FvM

    Points: 2
    Helpful Answer Positive Rating
Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top