here image shows my micro controller based project.
I need to drive large display so I have used uln2803 Ic.
also I need to multi plexing.
So I have used common anode to multiplex , but there I can't use relay.

I selected BC327 but I understood that I can't turn off it using 5v micro controller output because emmiter in 12V.

I need mosfet somthing really same as relay. when I give 5V it should turn on or off and for 0V it should do the inverse (on or off).
it's maximum current should be about 500mA because display needs 250mA when it fully lit.


any one can help me.

please suggest me a mosfet.
if there is IC which has 4 switches like I mentioned also very good because I need 4 mosfets.

thank you

 

First, you need a high-side driver, as discussed here.

Optionally, you can convert it to a PFET.

How much current does the high-side switch need to pass?

 

500mA. max. if it is more also about 350mA fine

 

yes I know I can use PFET. but I am not sure how. I am going to draw pcb and handover to manufactures. so I need your help

 

500mA. max. if it is more also about 350mA fine

For that, you dont need a PFET. A simple PNP switching transistor will do. Follow the link to see what else you need...

 

I need to do switching. So I like to use PFET (because I think they are good in high speed switching)

 

I saw the link. there you have used level shifter. will that circuits works fine for high speed switching. I mean switching speed should be enough past then eye can't see any flashing

isn't there any simple circuit like one FET ?

 

Why do you think you need high speed switching for multiplexing a display?
Do you understand how to follow a posted link?

Click on this

 

will this work?

 

Think about this: If you use a PFET, its source is tied to +12V.

What gate voltage is required to turn it off?

What gate voltage is required to turn it on?

 

I am new so please forgive me if I have done any mistake.
I click on the link and check that design.
it is looks good.
but supply is 24V
I think it can be adjusted.

 

W

...will this work?

Why do you think you need a power device like the IRF530 to do the level shifting?

What is the threshold voltage of a IRF530?

 

I am new so please forgive me if I have done any mistake.

Yes, and I am trying to get you to learn something instead of just handing you a ready-made answer...

I click on the link and check that design.
it is looks good.
but supply is 24V
I think it can be adjusted.

Yes it can.

 

ok.
I will use that design.
please confirm this for my knowledge.

there 2n3904 is the level shifter.
darlinton pair provides the sufficient current
am I correct?

is there any IC we can buy directly for this?

 

ok.
I will use that design.
please confirm this for my knowledge.

there 2n3904 is the level shifter.
darlinton pair provides the sufficient current
am I correct?

is there any IC we can buy directly for this?

Since you are switching only 500mA, a simple PNP like a 2n3906 will work.

 

...
is there any IC we can buy directly for this?

http://www.st.com/web/en/catalog/sense_power/FM1965/SC1037

http://www.linear.com/products/high_side_switches_*_mosfet_drivers

 

Since you are switching only 500mA, a simple PNP like a 2n3906 will work.

? Don't think so. It's rated for 200mA .

 

I turn towards this design
how it looks like?


http://electronics.stackexchange.co...t-way-to-get-5v-or-12v-or-0v-from-arduino-pin

get from this link

 

I dont like the emitter follower. That circuit is bad because the Ib =>Ic/10 is not even close to being full-filled...

Look at this sim. Note that this driver cannot supply 350mA.



Here is a fixed version, but look at the power dissipation in Q2



Back to the one I recommend: All of the base currents have the right ratios with respect to the collector currents. I selected the appropriate PNP for sourcing 350mA.

 

I need to do switching. So I like to use PFET (because I think they are good in high speed switching)

Typical display multiplex strobing is about 500Hz - you don't need fast for that.