IRF1404 Vgs th problem

Tip / Sign in to post questions, reply, level up, and achieve exciting badges. Know more

cross mob
User19846
Level 1
Level 1
First question asked
Hello,Is it difficult to turn off the MOS after it gets hot at work, because its Vgs(th) Max is only 4V
0 Likes
1 Solution
Abhilash_P
Moderator
Moderator
Moderator
50 likes received 500 replies posted 250 solutions authored

Hi,

Yes , at some point if the current is too much it becomes difficult to turn OFF the MOSFET when it is hot enough. IF the Vds times Rdson is sufficiently large enough,
the MOSFET continues to conduct even when the gate to source voltage (Vgs) is turned OFF.

If Vgs low isn't low enough to turn the MOSFET off, it will still be carrying current but probably also dropping some of the supply voltage that should warm up or even get hot.

A proper heat sink must be designed in this condition to avoid this issue.

The following image helps you in understanding leakage currents during increase in MOSFET temperature and maintaining zero gate to source voltage (Vgs=0)

Abhilash_P_0-1667368891544.png

But since the currents are in the order of uA, it wont affect much. 


Regards,
Abhilash P

View solution in original post

0 Likes
1 Reply
Abhilash_P
Moderator
Moderator
Moderator
50 likes received 500 replies posted 250 solutions authored

Hi,

Yes , at some point if the current is too much it becomes difficult to turn OFF the MOSFET when it is hot enough. IF the Vds times Rdson is sufficiently large enough,
the MOSFET continues to conduct even when the gate to source voltage (Vgs) is turned OFF.

If Vgs low isn't low enough to turn the MOSFET off, it will still be carrying current but probably also dropping some of the supply voltage that should warm up or even get hot.

A proper heat sink must be designed in this condition to avoid this issue.

The following image helps you in understanding leakage currents during increase in MOSFET temperature and maintaining zero gate to source voltage (Vgs=0)

Abhilash_P_0-1667368891544.png

But since the currents are in the order of uA, it wont affect much. 


Regards,
Abhilash P

0 Likes