Low power micro switch MOSFET transistor tutorial

[slimest]

nicotime, RDS-ON is the resistance of the fully opened mosfet. Lower the RDS-ON, lower power (and voltage) loss on it. For our purposes RDS-On 5-10-40 mohm is OK. Typically 10 mohms.
But I told about another thing (sorry, jhonuts). There is another very important parameter of mosfets - voltage on Gate which fully opens the transistor and gives us this low RDS-On. These voltages are different for different mosfets. And if you look at the datasheet, you have to find the VGS - voltage between gate and source, which provides fully opened mosfet (lowest RDS).
Oh, my poor English

P.S. Sometimes it's difficult to find the VGS in datasheet because this parameter is gradual. In this case watch a graphic which shows relation between the source-gate voltage and source-drain resistance.

I use IRLML6402 transistors in common. They are small enough and quite reliable even if I switch a step-up board with it. And, as a matter of fact, they fit perfectly to repair a burnt eGo boards: just desolder the dead mosfet and put IRLML6402 instead. Now your board will be something like Terminator-2

 

[jhonutz]

Do I connect the mosfet to the (-) in or out of the LM2596 regulator? I normally use 12 v 5amp source in and 5 to 6v out.

The best is to use EN pin from LM2596, and to put that pin to ground to start regulator.In that case you may use a small mosfet, because will cross only maximum 10 mA.If you put mosfet to IN our OUT need a relative big mosfet to handle with 2-3A.

Anyway to answer at your question put to IN if this is what do you want.

 

[nicotime]

nicotime, RDS-ON is the resistance of the fully opened mosfet. Lower the RDS-ON, lower power (and voltage) loss on it. For our purposes RDS-On 5-10-40 mohm is OK. Typically 10 mohms.
But I told about another thing (sorry, jhonuts). There is another very important parameter of mosfets - voltage on Gate which fully opens the transistor and gives us this low RDS-On. These voltages are different for different mosfets. And if you look at the datasheet, you have to find the VGS - voltage between gate and source, which provides fully opened mosfet (lowest RDS).
Oh, my poor English

I see...make sense...oops...I missed jhonuts post about that...thanks guys!

 

[jhonutz]

nicotime, RDS-ON is the resistance of the fully opened mosfet. Lower the RDS-ON, lower power (and voltage) loss on it. For our purposes RDS-On 5-10-40 mohm is OK. Typically 10 mohms.
But I told about another thing (sorry, jhonuts). There is another very important parameter of mosfets - voltage on Gate which fully opens the transistor and gives us this low RDS-On. These voltages are different for different mosfets. And if you look at the datasheet, you have to find the VGS - voltage between gate and source, which provides fully opened mosfet (lowest RDS).
Oh, my poor English

P.S. Sometimes it's difficult to find the VGS in datasheet because this parameter is gradual. In this case watch a gpaphic which shows relation between the source-gate voltage and source-drain resistance.

Lower RDS-ON means you don`t have a lot of dropout voltage..

 

[BJ43]

nicotime, RDS-ON is the resistance of the fully opened mosfet. Lower the RDS-ON, lower power (and voltage) loss on it. For our purposes RDS-On 5-10-40 mohm is OK. Typically 10 mohms.
But I told about another thing (sorry, jhonuts). There is another very important parameter of mosfets - voltage on Gate which fully opens the transistor and gives us this low RDS-On. These voltages are different for different mosfets. And if you look at the datasheet, you have to find the VGS - voltage between gate and source, which provides fully opened mosfet (lowest RDS).
Oh, my poor English

P.S. Sometimes it's difficult to find the VGS in datasheet because this parameter is gradual. In this case watch a graphic which shows relation between the source-gate voltage and source-drain resistance.

So will the one I bought open completely with a 12+volt source and the 47k resistor?

 

[slimest]

BJ43, with 12V source it will obviously work. With ANY resistor. Solder 10k or 100 k - no difference at all.

 

[jhonutz]

It`s a lot o history on ECF about mosfet`s . It`s so simple to use this transistor....

@BJ43 you want to vape at your car battery , put your back in and walk to street and vape

 

[BJ43]

The best is to use EN pin from LM2596, and to put that pin to ground to start regulator.In that case you may use a small mosfet, because will cross only maximum 10 mA.If you put mosfet to IN our OUT need a relative big mosfet to handle with 2-3A.

Anyway to answer at your question put to IN if this is what do you want.

Thanks but I use the preassembled LM2596 boards from China and I don't want to desolder or cut any pins as I am not very good in electronics, that is why I thought just a mosfet switch...

 

[jhonutz]

So use a mosfet Dpack capsule or TO220 capsule will be enough.Works well and TO223 and it`s a little smaller.

 

[BJ43]

So use a mosfet Dpack capsule or TO220 capsule will be enough.Works well and TO223 and it`s a little smaller.

Lol you write to me like I understand what you talk about. If I were younger I would study up on some electronics, but neither of my two 70 year old heads are fully functional.