I have one simple question about the MOSFET. Can N-Channel MOSFET(BSS138) able to switch the (DC) 5V 1A load/line ? (Input to mosfet will be the 3.3V from MCU).

Below is the image of connections. Here LV,LV1 will be controlled by the microcontroller. (LV = 3.3V,LV1 = 3.3V,HV = 5V, so when LV1 = 0V then on HV1 we will get 0V and if we apply 3.3V to LV1 then HV1 will be the 5V but I am not sure that BSS138 can tolerate the 1A on HV line)

But I have the question for the HV line. I am sure that 5V on HV can be tolerated by the BSS138 but can it tolerate 1A current on HV line ?

Thanks in advance


simulate this circuit – Schematic created using CircuitLab

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    \$\begingroup\$ Nope, read the datasheet, continous Id (Drain Current) = 0.22 A which is too low for 1 A. Explain why you could not have figured this out yourself. \$\endgroup\$ – Bimpelrekkie Dec 11 '17 at 11:16
  • \$\begingroup\$ Hi @Bimpelrekkie thanks for your comment. I couldn't because I am not sure about the electronics behind MOSFET. \$\endgroup\$ – Bhautik R. Dec 11 '17 at 11:29
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    \$\begingroup\$ We are not here to read the datasheet to you. \$\endgroup\$ – Olin Lathrop Dec 11 '17 at 11:42
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    \$\begingroup\$ This is a logic level shifter. I am wondering why you have 1A on it. Looks like an X-Y problem to me. \$\endgroup\$ – Trevor_G Dec 11 '17 at 12:41
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    \$\begingroup\$ (1) The unit symbols for Volt and Ampere are 'V' and 'A', not 'v' and 'a'. (2) Current is not on a line; it goes through a line. (3) You are asking about a current of 1A "on" (through) the HV line. Note that there is a 10kOhm resistor in series. 1A going through that line would mean that there are 10kV across this resistor and a power dissipation of 1kW. \$\endgroup\$ – Curd Dec 11 '17 at 13:44

The BSS138 is rated for an absolute maximum drain current of 0.22A, so no you cannot switch 1A with it. You need to find a MOSFET that will take a drain current of 1A (absolute minimum - preferably more to have some headroom) and ensure that the power dissipated in the package does not take it above (or near) its maximum operating temperature. On top of this, ensure that the gate turn on voltage (Vgs threshold) means it will be turned on by 3V3.

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  • \$\begingroup\$ hi @DiBoco thanks for your answer, I appreciate the quick response. I just added more details on the question with image. Could you please check it again ? Thanks \$\endgroup\$ – Bhautik R. Dec 11 '17 at 11:31
  • \$\begingroup\$ Your schematic makes no sense to me, but the fact remains you cannot pass 1A through that MOSFET. I don't think you understand at all how a MOSFET works and need to read up more on them. \$\endgroup\$ – DiBosco Dec 11 '17 at 11:36
  • \$\begingroup\$ Yes you are right, I need to study MOSFET in deep. \$\endgroup\$ – Bhautik R. Dec 11 '17 at 11:39
  • \$\begingroup\$ you need to study Ohm's law first \$\endgroup\$ – jsotola Dec 12 '17 at 2:29

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