Hi,
Have a circuit where i would like to get rid of the Relay.

So i came up with this.
Will it be possible, or do the P-Channel Mosfet need 0 v = on and 12v= Off. ???

And one q more.

Can i just use the 2 diodes to control 2 inputs ?

 

Here is a P-channel mosfet (as you draw):



Notice the body diode! It will always be conducting.

If you mean an N-channel mosfet, it will not turn on in that configuration until Vgs > Vdrain or Vcc (i.e., 12 V as shown) plus whatever Vgs is specified for being fully on.

EDIT: Since BUZ172 is a P-channel mosfet, swap the Drain and Surce connections. Then when Vg = 12 V relative to ground (i.e., Vgs = 0 v relative to source), the mosfet will be off. When Vgs = -12V (i.e., gate is cnnected to ground), then it will be on.

 

This is typical.

It is not good practice to put 12 volts directly on a LED.

 

Ok, the LED is just for showing loads.,, it's a 12v bulp.
I need the construction to have load on 12v side, and the GROUND is on BULP, and therefor not able to change.

Edit. 12v = ON . 0v = OFF

 

GROUND is on BULP, and therefor not able to change.

Utter confusion seems to be reigning.

What is "BULP?"
What mosfet do you actually intend to use? N-channel or P-channel? Your diagram seems to show a BUZ172. That is a P-channel mosfet.
Do you understand which pins are which on each variety of mosfet?

About the only thing that is clear is you want the mosfet to sink current from the load. That can be done with either variety of mosfet, but is often simpler to do with a P-channel version.

 

0V = 12 volts from S to G on the P-MOSFET = on.

 

Sorry for bad english,

light bulb

The "light Bulb" has to be on the "output" from the curcuit.
Have 12v in, and the gate voltage is 0 v or 12 v , prefer 12v to be on.

edit, since last post, how to change the gate voltage to oppesite. ?

 

Sorry for bad english,

light bulb

The "light Bulb" has to be on the "output" from the curcuit.
Have 12v in, and the gate voltage is 0 v or 12 v , prefer 12v to be on.

edit, since last post, how to change the gate voltage to oppesite. ?

ON = Vsg =12 V or Vgs = -12V The latter is a more common expression. In other words, the device is ON when the gate is at ground potential.

OFF = Vgs = 0 V That is, the gate is at 12 V relative to ground.

You cannot change the physics. Theoretically, your gate driver could do the inversion.