Should I choose MOSFET with Rds lowest or P(dissipation) lowest?

[lemta2000]

I'm looking for a MOSFET for save power. so, should I choose Rds on lowest or P dissipation lowest. Is Rds on low that mean Pd low?

thanks!

 

[keith1200rs]

You need to look at the ON resistance not the power rating of the device. The power rating is a measure of how much the device could safely dissipate not how much it will dissipate.

Keith

 

[palmeiras]

Hi lemta2000,

If you want low power dissipation, do as keith suggest you, “decrease its ON resistance". For that, you need to increase the transistor width, when the Ron = 1/uo*Cox*W/L*(VGS-VT).
In order to have lowest capacitances, use the minimum value of transistor length allowed by the technology.
Regards,

 

[Tahmid]

Hi,
You should choose a MOSFET with lowest Rds(ON). Power dissipated in the MOSFET = I*I*Rds(ON). The Power dissipation rating of the MOSFET is the maximum power it can dissipate without getting damaged. The lower the Rds(ON) the lower the power dissipated within the MOSFET. You could also reduce overall Rds(ON) by paralleling MOSFETs.

Hope this helps.
Tahmid.