Mosfet is not turning off at high frequency

Thread Starter

Arunmosespaul P

Joined Apr 11, 2019
9
Hi i am using a driver for driving MOSfet.
Driver output is perfect square wave. But mosfet output is not perfect at high(100khz) frequency.IMG_20190411_165653644.jpg IMG_20190411_165608475.jpg IMG_20190411_165559230.jpg
 

DickCappels

Joined Aug 21, 2008
8,831
crutschow wrote "Post #3"

Thank you. Don't know what I would do if you weren't here.

Suggestion: Try reducing the gate series resistor to 10 to 20 ohms. Also, can you show the gate signal, or is that the gate signal in post #8?

If it is the drain signal, the your MOSFET is not turning all the way on quickly.
 
Last edited:

BobaMosfet

Joined Jul 1, 2009
2,002
Put a trace on your gate and on your load and see if load follows gate. If so, it's because your gate is a capacitor, and you're seeing reactance in action at the frequency you're operating at. You may need to choose a mosfet with different gate response.
 

bertus

Joined Apr 5, 2008
21,940
Hello,

In the application schematic in the datasheet of the driver, there is no resistor between the driver and gate.
The resistor will cause a delay in conjunction with the gate capacitance.

Bertus
 

shortbus

Joined Sep 30, 2009
9,441
Is there a pull down resistor from gate to source? A "block diagram" isn't a schematic, so it's hard to tell what the circuit actually is.
 
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