How to use P- and N-channel Mosfet as switches

[fixation]

hello everybody,

im my amplifier I want to use mosfet to disconnect the powersupply lines in case of an error, this error could be DC-fault, temp fault etc. I have an ATmega which will be controlling the Amplifier.

Normally this would be done with relays but i don't like the "clicking noise" they make.

So i would like to try a different approach by using mosfets as a switch.

An externally hosted image should be here but it was not working when we last tested it.

can someone please tell me how i should connect them? What i would like is that A and B will be replaced with a mosfet + additional components ( level shifter etc)

which mosfet needs to be where and how do i connect them?

Best Regards Fixation

 

[richie00boy]

Either use n-channel for both and isolated gate drivers, or p-channel in the +ve line and n-channel in the -ve line and refer the gate drive to ground.

 

[CBS240]

I would think you want to choose fets with lowest Rds on, and placed in the circuit after the filter caps. Totem pole driven N-channels? IRFZ44 is a cheapie, used in low voltage(hi current) SMPS switch.

 

[ilimzn]

...remembering that the maximum gate potential is 20V for most MOSFETs. Working as a swuitch comes naturally to MOSFETs

 

[jackinnj]

You can use something like this although you will have to change the values to real-world

 

[fixation]

I think i will go with the n-channels with isolated gate drivers.
If i would put another small transformer in my amplifer which could power an MAX621 which power for example an IRF540

.. does that mean that it is isolated from the rest of the circuit?

Could i use the MAX621( High side driver ) for +ve line?
and do i need to get a Low side driver for the -ve line? or could i use a High Side driver here aswell?


the mosfet will be placed after the capacitator bank as CBS240 said

@jackinjj: Your circuit looks good but it uses 2 mosfet. the problem is that I want to use this circuit for 7 channels.. which means that i should use 28 mosfet....

i'd rather go with a solution that uses some IC's

 

[Upupa Epops]

All that solution isn't so easy, how do you think...probably will arise something, which will be more comlicated than " guarded " amp...