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Mosfet Transistor Datasheet

kitstudent

New Member
Hello!

Can somebody help me read the datasheet of a mosfet?

I want to find out, in what manner the Vgs behaves in relation to the Id? I thought Figure 3 would give me the relation between voltage and current but I am not quite sure, how to read the diagram.. Does it for example mean that, if I put on Vgs=4.5V, I get an current from source to drain of 10 Amps if Vds=1V?

My teacher also said sth about control circuit vs main circuit. As far as I understand, the control circuit would be the circuit in which the mosfet is activated, meaning that a certain amount of voltage (Vgs) is required to let current flow from source to drain.

And the main circuit would be the circuit that actually includes the components through which the current shall flow.. Am I correct?

I'd appreciate every help!
 

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danadak

Well-Known Member
Most Helpful Member
Does it for example mean that, if I put on Vgs=4.5V, I get an current from source to drain of 10 Amps if Vds=1V?

Yes, but notice those are typical values, and current depends on what
the load will allow to flow. The graph shows what would flow if the
terminal voltages are met in the graph. Both MOSFET and load determine
what current will flow in the actual circuit. Example of a load line analysis :

1661083900602.png


Regards, Dana.
 
Last edited:

audioguru

Well-Known Member
Most Helpful Member
A transistor like that Mosfet has a wide range of specs. The graphs are for "typical" ones but you cannot buy a typical one, you might get a "minimum" specs one or get a "maximum" specs one.

The datasheet says that a Vgs of 10V causes all of the Mosfets with that part number to turn on very well, a Vgs of 6V turns on some of them fairly well but others conduct very well.
The threshold Vgs voltage where the Mosfet conducts such a low current (250uA) that it is almost turned off is 2.2V for some to 3.9V for others.
Then with a Vgs of 4.5V a sensitive one conducts some current but others are almost turned off.
 

Papabravo

Well-Known Member
The way you want to interpret Fig. 3 depends on your purpose. Using it as a switch you want to let the load determine the actual drain current and you want to minimize the losses which means going for the smallest rds(on) you can get. This means go for a Vgs of 15 V to turn the device on hard. If you are using it as an amplifier, then you may have other considerations.
 

audioguru

Well-Known Member
Most Helpful Member
The graphs only apply to a transistor that has "typical" specs. The ones you buy might have minimum or maximum specs.
 

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