Pls suggest low threshold VGS mosfet


I am driving a mosfet as a switch using GPIO pin of atmega328 running off 2AA cells. The circuit is logically similar to this

I ve tried BS250P however the load is not totally switched on probably because the mosfet's Vgs is too high and the AA cells voltage is less to drive the gate. Can you please suggest some other P-channel mosfet that are easily available.

Thanks and Regards, WonderfulIOT

Look for logic-level MOSFETs, usually has an L in the model number

Vthr is not relevant to switching on, only to switching off. You want Vthr to be above 0.0V, so not too

The thickness of the gate oxide is less for low-voltage logic MOSFETs, leading to a smaller difference
between Vthr and the plateau voltage, but to be honest power MOSFETs are a lot more complex
with 3-dimensional structure so low-voltage performance is a complex function of this structure as
well as oxide thickness.

This is why you just need to search for the Vgs value quoted for Rds(on) - many electronic suppliers
have search engines to help you do parametric search on devices like this.

What switch current are we talking about, and for how long. Maybe a PNP transistor is a better option. You might get a saturation voltage of ~0.2volt.

You could also select a bunch of P-fets you're using now for the lowest Vgt with a DMM. Connect gate to drain. DMM on diode measurement. +lead to source, -lead to drain. Read Vgt voltage. Needs to be lower than ~1.5volt. Leo..

BTW nearly all the very low voltage power MOSFETs are surface mount, and there’s a lot more
choice in n-channel than p-channel.

OP did not say what is being switched and why high-side switching is needed. Leo..