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# Forward Current through the Body diode of mosfet when its OFF

Level 1
Level 1

Hello

We are using the P channel MOSFET IRLM5103 two switch the 12V for the analog Application. the voltage is switched from Source to drain when the MOSFET is ON.  Also when there is 154V volt at the input (Drain) then there will be 12.5V constant at the output (Source) of the depletion mosfet. due to which the the body diode of the IRLM5103 will be the forward biased and the some of the current will flow to the +12V source. how much current will flow through the body diode when that body diode will forward biased ? what will impact on the +12 Source ?

I have attached the schematic of the application.

1 Solution

# Re: Forward Current through the Body diode of mosfet when its OFF

Level 1
Level 1

Hello sushank,

Thanks for the reply , i can check that in simulation but i need that reverse current to be calculated in my calculation. for that how should i consider the drop across the diode its not given in the datasheet for the low leakage current.

I have checked the actual result as well there, I got 12.5V as output at source of the depletion MOSFET and the current which is flowing through the body diode of IRLML5103 is of 198uA at 85 deg. but in calculation how can i consider the drop of Body diode ?

5 Replies

# Re: Forward Current through the Body diode of mosfet when its OFF

Moderator
Moderator

Hi there,

in the simulation itself you can check the drain current, negative current will be the body diode current.

Thanks.

# Re: Forward Current through the Body diode of mosfet when its OFF

Level 1
Level 1

Hello sushank,

Thanks for the reply , i can check that in simulation but i need that reverse current to be calculated in my calculation. for that how should i consider the drop across the diode its not given in the datasheet for the low leakage current.

I have checked the actual result as well there, I got 12.5V as output at source of the depletion MOSFET and the current which is flowing through the body diode of IRLML5103 is of 198uA at 85 deg. but in calculation how can i consider the drop of Body diode ?

# Re: Forward Current through the Body diode of mosfet when its OFF

Moderator
Moderator

hi,

is D2 the body diode you are referring, because you dont need to place separate diode as body diode.

# Re: Forward Current through the Body diode of mosfet when its OFF

Level 1
Level 1

Hello ,

that i placed for the Understanding or the visibility because in ltspice there is no any body diode shown in the symbol so i added for the understanding its integrated body diode only.

# Re: Forward Current through the Body diode of mosfet when its OFF

Moderator
Moderator

Unfortunately,  there is no hard and fast rule to calculate and formulate the body diode current. if still you want to formulate the current than you need to prepare equivalent circuit in reverse mode when diode comes in action and apply the KCL. make sure that in formulation time dependency should be there.

Thanks.