Selecting the proper MOSFET for a 5VDC, 145 milliamp relay load.

Other Hardware General Electronics
1

Hello, I am using a 5VDC circuit where I need a P channel MOSFET with the following characteristics:
Drain current at least 200 ma - Drain to Source voltage at least 8 volts . I looked up NTE's datasheet and it lists several MOSFETS but the Drain to Source voltage says 55 Min or 100 Min, or 200 Min. I'm assuming (Min) means minimum? So these MOSFETS are not suitable for a 5 VDC supply? Am I reading this wrong? Can anyone help me to find a part number of a MOSFET thats meets my needs? Any help would be appreciated.

2

Look at DMP2045UQ-7

Can switch on/off with a 5v signal, 0.05ohm on resistance.

https://www.digikey.com/en/products/detail/diodes-incorporated/DMP2045UQ-7/10674156?

3

55 Min means that it will handle at least 55 volts, maybe more. 5 volts is less than 55 volts so it will be fine.

4

In general the higher the breakdown voltage of a MOSFET the larger the on-resistance, so normally
you'd aim for a breakdown voltage about twice the maximum voltage present in the circuit for a
reasonable level of safety margin. However 20V is about the lowest rating you'll ever see and 0.145A
isn't a demanding load so you'll be fine with the 55V MOSFET so long as its logic-level - this is
vital.

Say you find a MOSFET with a 0.1 ohm on-resistance at Vgs=5V, this would do as the dissipation
in the MOSFET is I-squared-R = 0.1450.1450.1 = 2mW (ie it will run very cool!).

Logic level MOSFETs have an on-resistance rating given for Vgs = 5V (or less, such as 4.5V). If
the on-resistance is only quoted for 10V, its not logic level.

For a low current like 0.145A, a simple BJT switching transistor such as a 2N2222A will also
be completely fine. A base resistor (330 ohm or so) would be needed for a BJT, note.

Either way you need a free-wheel diode across the relay coil however its switched.

5

Thank You for your replies.

6

. I looked up NTE's datasheet and it lists several MOSFETS but the Drain to Source voltage says 55 Min or 100 Min, or 200 Min.

As others said, the 55v min is a specification of the maximum the device can handle.

Think of it as .... a rope has a RATED strength of 200# minimum (it could be more but the mfg guaranteed it will be at least 200#.

And you wish to hold up your bicycle which is 20#.

In my opinion NTE devices are of significantly inferior quality. This is based on past experience.