Is this a good way to test a mosfet? :-)

Other Hardware General Electronics
1

I made this circuit:

VPotFet2 - is for measuring V across gate & ground. The black and yellow leads are the ones I used to measure the voltage across the gnd & gate:

VPotFet2.jpg
VPotFet2.jpg800×1157 80.3 KB

VPotFet1 - is for measuring V across drain & source. Once again the black and yellow leads are the ones measuring the voltage across the resistor out the drain in this case in red downstream from the mosfet and the resistor and across the resistor by the black lead that connects to ground.

VPotFet1.jpg
VPotFet1.jpg800×1251 86.8 KB

What I did was, turn the POT down to 0. Then placed the multimeter leads across the resistor (downstream from the mosfet). I turned the pot up until the voltage across the resistor read 2.3V. I disconnected the yellow/black leads and put them over the gate and read 1.2V.

So with 1.2V at the gate I got 2.3V at the pot. Vsource was 8.8V 6xAA battery pack.

Mosfet is IRLB8721 which has a Vth of 1.35V.

VPotFet2.jpg
VPotFet2.jpg800×1157 80.3 KB

VPotFet1.jpg
VPotFet1.jpg800×1251 86.8 KB

2

  1. The pictures are quite messy and you don't include the whole project.

  2. You didn't include the name of the transistor or link its datasheet.

  3. What is your question?

3

If the question is from the title, "Is this a good way to test a mosfet?"

What are you testing?

You are operating the mosfet at this low gate voltage in the ohmic region, (linear region). The mosfet is just working like a big variable resistor and wasting lots of power. Luckily you are limiting current with the resistor of some unknown value.

At higher power levels this is a good way to destroy a mosfet.

4

Mosfet datasheet should have test circuit

  1. You didn't include the name of the transistor or link its datasheet.

No. It is not a good way to test a mosfet.

There's your answer.

Give us more information and will give you more.