Suitable MOSFET's for H-bridge

Thread Starter

8dm7bz

Joined Jul 21, 2020
171
Hello,
I designed a circuit in LTSpice and wondered wether or not it would work as I expect it, or if there are any problems with it. I expect the current to be at around 260mA peak. As for the real MOSFET's I would be using: DMG1012 as the n-channel, and the DMG1013 as the p-channel MOSFET. I choose those two because they have a rather low gate capacitance.
Two questions I have right off the bat is:
1.) Could I switch them with a 5V gate voltage ? I'm asking because the datasheet states that the maximum voltage between the gate and the source is +-6V, but then later it says "Gate Threshold Voltage" should be between 0.5V and 1V.
2.) How important is it to match the MOSFET's, and what exactly does it mean to match them ?

-8
 

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ericgibbs

Joined Jan 29, 2010
11,551
hi 8d,
The two d/s shows that at 5V Vgate drive they will be OK.
I would say for you low current application, matching is not a problem.
E

Update:
This txt file has the Spice models for the DMG's
 

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Last edited:

Thread Starter

8dm7bz

Joined Jul 21, 2020
171
Great, after some headaches I got it to work. Thank you very much.

After I implemented the design with the new MOSFET's I tried changing the 5V gate voltage to 3.3. It still works in the simulation. Is that expected or am I overlooking something. 3.3V is favoured, because otherwise I need to level shift the signal. And also I guess I'm only talking about the p-channel MOSFETs.
I understand that a certain gate to source voltage has to be present in order to activate. But when does it deactivate ? Lets say I drive the gate voltage to 3.3V, then the gate to source voltage is at -1.7V (my presumption is that the source is at 5V).

Could I drive this circuit with 3.3V at the gate ?

Note for the attached picture: 10 is drain, 20 is gate, and 30 is source
 

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Thread Starter

8dm7bz

Joined Jul 21, 2020
171
Great thank you :)

I packed all the files into the attachment. It consists of two .asy files and two .lib files. To use those, put the .lib files into your lib/sub/ folder. Then put the .asy files into your sym/AutoGenerated/ folder. Now you should see those two components in LTSpice under "AutoGenerated". That's how I did it anyways.

-8
 

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ericgibbs

Joined Jan 29, 2010
11,551
hi.
If you would prefer the standard MOS symbols for the yellow boxes.

1. Right click on the circuit yellow boxes, on the circuit

2. Left click Open Symbol, this should open the asy file.

3. Use F5 to delete the yellow area.

4. Use F7 to move the 10, 20 and 30 to the place where the MOS FET is usaully drawn

5. Use the 'L' key draw the MOSFET symbol lines.

Save the asy file as you go, the circuit drawing should match the asy model.

E

WIP, example of the changes, needs to be completed.
 

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