First situation (Q1 and Q3 get 5V):


Second situation (Q2 and Q7 get 5V):


As you see R9 just gets 0.95V or -0.95V, but the bridge is powered with 12V.
And I know why this happens, the saturation of a MOSFET is defined by the voltage between the gate and the source (Vgs) and since the voltage at the source of Q1 and Q2 depends directly on the transistors below, this does not work as it should. I'm probably wrong and that's why I'm doing this thread, any information is very useful to me!

 

Hello,

The input voltages are to low to drive the fets.
Try to drive them with 12 volts and see the results.

Bertus

 

You must drive gates by diagonal, not in vertical

EDIT: Q1+Q7 or Q2+Q3

 

Since Q1 and Q2 are N-channel devices they operate as voltage followers and will drop a lot of voltage, depending upon the actual transistors.

If the top two transistors (Q1 and Q2) are changed to P-channel and driven properly with 12V P-P you can get a higher voltage across the load, and also get the bonus of lower DC voltage across the load.

 

The top P-MOSFETs are upside down.
Their sources must be connected to the positive voltage.

To determine if a MOSFET is connected properly, note the direction of the substrate diode arrow.
They must always be reversed biased in normal operation.

 

Hello,

The input voltages are to low to drive the fets.
Try to drive them with 12 volts and see the results.

Bertus

I need it to be 5V

 

You must drive gates by diagonal, not in vertical

EDIT: Q1+Q7 or Q2+Q3

That's for H-bridges with ony p-channel or n-channel transistors

 

Hello,

I need it to be 5V

Then put a transistor between the 5 volt input and the bridge to bring it up to 12 Volts.

Bertus

 

Hello,

Here I found a H-bridge for 12 Volts with opto coupler inputs:
https://onebyzeroelectronics.blogspot.com/2016/03/how-to-make-simple-h-bridge-from-mosfet.html

Bertus

 

Hello,

Then put a transistor between the 5 volt input and the bridge to bring it up to 12 Volts.

Bertus

It works, but the whole point of using an H-bridge to use higher voltages is lost

 

Hello,

Here I found a H-bridge for 12 Volts with opto coupler inputs:
https://onebyzeroelectronics.blogspot.com/2016/03/how-to-make-simple-h-bridge-from-mosfet.html

Bertus

Maybe I'm searching for something that's not real XD

 

I need it to be 5V

Then use logic level N channel MOSFETs and drive P channel power MOSFETs with an N channel logic level device. Where is this 5V coming from?

 

Since Q1 and Q2 are N-channel devices they operate as voltage followers and will drop a lot of voltage, depending upon the actual transistors.

If the top two transistors (Q1 and Q2) are changed to P-channel and driven properly with 12V P-P you can get a higher voltage across the load, and also get the bonus of lower DC voltage across the load.

Yeah, I just wanted to drive them with 5V but now I'm realising that's not possible, at least in this way

 

Then use logic level N channel MOSFETs and drive P channel power MOSFETs with an N channel logic level device. Where is this 5V coming from?

AND logic ports

 

AND logic ports

So doesn’t that suggest to you that you need logic level MOSFETs?

 

The top P-MOSFETs are upside down.
Their sources must be connected to the positive voltage.

To determine if a MOSFET is connected properly, note the direction of the substrate diode arrow.
They must always be reversed biased in normal operation.

Yeah! That way the bridge works better, thanks!

 

So doesn’t that suggest to you that you need logic level MOSFETs?

I didn't even know they existed! Ok I'll test that

 

Below is a simple way to drive an H-bridge from a 5V signal (assuming the bottom N-MOSFETs are logic-level type) with a 12V supply.

.

 

So doesn’t that suggest to you that you need logic level MOSFETs?

One question, should I look for 5V in Vgs or Vgs threshold?

 

Below is a simple way to drive an H-bridge from a 5V signal (assuming the bottom N-MOSFETs are logic-level type) with a 12V supply.

View attachment 235396.

Oh, cool, I'll study that