IRF640 LTspice model

Thread Starter

manal abdelmageed

Joined Dec 20, 2022
6
i was looking for a model of IRF640 mosfet for LTspice but Unfortunately there was something about the model
T on is very large (about 60 micro) so i was wondering if anyone could help me to find another one
 

Papabravo

Joined Feb 24, 2006
21,159
I don't think that (T on) is one of the parameters can you post the ".model" card you have or the .subckt that you think is erroneous?

ETA: I have 3 different .subckt models that you can use.
 

Thread Starter

manal abdelmageed

Joined Dec 20, 2022
6
I don't think that (T on) is one of the parameters can you post the ".model" card you have or the .subckt that you think is erroneous?

ETA: I have 3 different .subckt models that you can use.
It was just an indication for me that something is wrong about the model
Could you please post the models you have !?
I will try them because unfortunately I don't have an experience about LTspice in general so I'll try the models to choose one
 

Papabravo

Joined Feb 24, 2006
21,159
It was just an indication for me that something is wrong about the model
Could you please post the models you have !?
I will try them because unfortunately I don't have an experience about LTspice in general so I'll try the models to choose one
I can do that, but I would like to understand why you think there is a problem. If I can see what you are working with, I may be able better help you. The best thing to do is bundle up everything you are working with so I can see what you are seeing. This is BECAUSE you are not experienced with LTspice and I don't want you running down rabbit holes you don't need to go down. This will also be a good experience when you run into future problems.
 

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Thread Starter

manal abdelmageed

Joined Dec 20, 2022
6
I can do that, but I would like to understand why you think there is a problem. If I can see what you are working with, I may be able better help you. The best thing to do is bundle up everything you are working with so I can see what you are seeing. This is BECAUSE you are not experienced with LTspice and I don't want you running down rabbit holes you don't need to go down. This will also be a good experience when you run into future problems.
I have an assignment in college to simulate a circuit which we had built before in the lab, this circuit by hardware had a T on about 3 micro seconds but when I tried to build a simulation for it the T on was 60 micro seconds which was very far about the real value
You could find the circuit attached to this reply, it's a very simple one in fact.
 

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Papabravo

Joined Feb 24, 2006
21,159
I have an assignment in college to simulate a circuit which we had built before in the lab, this circuit by hardware had a T on about 3 micro seconds but when I tried to build a simulation for it the T on was 60 micro seconds which was very far about the real value
You could find the circuit attached to this reply, it's a very simple one in fact.
You keep mentioning "T on", with a value of either 3 μsec or 60 μsec, but I have no idea what you are talking about. send me the actual files and not some !@#$%^&*() image.

ETA: A voltage source with zero rise and fall times is a Bozo no-no in simulations
 

Papabravo

Joined Feb 24, 2006
21,159
I think I see your problem. The gate resistor of 1kΩ is so large that the MOSFET cannot turn on and off in such a short time. This has absolutely nothing to do with the model or the subcircuit. I wish you had just done what I asked you to do in the first place. See the following simulation.

1671674045662.png

You can see from the green trace that the MOSFET is not able to turn on as quickly as you might like. Try a value for R2 of 10Ω. It is the gate capacitance in combination with the 1kΩ resistor that is causing the problem.

ETA: Yup, 10Ω works a whole lot better.
 

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Thread Starter

manal abdelmageed

Joined Dec 20, 2022
6
I think I see your problem. The gate resistor of 1kΩ is so large that the MOSFET cannot turn on and off in such a short time. This has absolutely nothing to do with the model or the subcircuit. I wish you had just done what I asked you to do in the first place. See the following simulation.

View attachment 283602

You can see from the green trace that the MOSFET is not able to turn on as quickly as you might like. Try a value for R2 of 10Ω. It is the gate capacitance in combination with the 1kΩ resistor that is causing the problem.

ETA: Yup, 10Ω works a whole lot better.
oh thank you a lot it's super useful answer
 

Papabravo

Joined Feb 24, 2006
21,159
I knew, but I was asked:

In fact, TS's problem is not in IRF640 model,
but in parameters of input pulse:
View attachment 283674
Quite right. Also in the 1000Ω gate resistor. It does not work well with a pulse that has a Ton of 3μsec with a period of 6μsec. There is just no time for the gate capacitance to be charged and discharged. It is mildly interesting that it will let you specify the source that way and it causes no problems if it is not connected to anything.

I remember back to my days as a novice programmer. Bugs were never my fault; it was always a compiler (assembler) problem. Ah...until it wasn't.
 
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