# MOSFET 3.3v gate and source

I'm developing a battery powered device and I need some switch. I used some bipolar transistor but because of power consumption I decided to switch to MOSFET. The problem is that the current the MOSFET need to turn on and off is at 3.3v, equal to the tension of the high of the esp32 with which I intend to control them. How could I solve this problems? How should I design this circuit? Thanks for your help

Can you post a drawing of the bipolar transistor circuit, and tell us what transistor you used?

Generally, you would use a P-channel mosfet to switch the 3.3V power line. A 100K resistor would connect the gate to the source. The gate would be grounded to turn on the mosfet.

Get a MOSFET with logic level gate, which is rated to work at such low voltage. Most logic level MOSFETs are properly open at 4.5V or higher; not good enough. You need lower. If the datasheet gives an RDS, ON at lower values you're in business. There are MOSFETs that switch well at voltages as low as 1.8V (or -1.8V for a p-channel MOSFET).

For suggestions we need to know exactly what exact load you're switching (especially how much current) and whether it's a high side or low side switch.

Hello, essentially I need a way to use 3.3V GPIO pins from a teensy to control an LED light which takes 12VDC. I know that MOSFETs can be used as switches, however I don't know enough about MOSFETs to understand how you change them with the 3.3V? From what I understand, if you apply a voltage to the gate, then the Drain-Source becomes conducting, however I'm not sure how to ensure that the 3.3V is adequate enough to switch the MOSFET into the saturation region where the Drain-Source is essentially a short circuit. Any help is appreciated, thanks

I'm not sure how to ensure that the 3.3V is adequate enough to switch the MOSFET into the saturation region where the Drain-Source is essentially a short circuit.

You look at the data sheet for the FET and see what the on resistance often called Ron at the voltage and current you are interested in. Not many FETs will work that low but a few will.

Plenty of choice when it comes to MOSFETs that switch very well at 3.3V. I just took delivery of a pMOS that's rated on at -1.8V VGS for use in a 3V battery powered project.

On the other hand, there is not much choice (please let me know if you find any) that are not in SOT-23 or similarly sized SMD package. The IRLB8721 looks promising and appears to conduct quite well at that low gate voltage (limited to about 10A), yet the datasheet does not explicitly list an RDS, ON below 4.5V...