I current have 3.6mA going down a wire, but I need to get up to 5A to drive a large device. I've heard I can use drivers to do this. I came across a Darlington Array but I'm not sure I how to implement this. Any ideas or suggestions of where to look would be great.

 

What is the supply voltage for the high current load? (Where does the 5A come from?)
What is load resistance? (Or what is the load?)

 

Here is a picture of my circuit

http://imgur.com/iRAeggf

The blue marker is where I need the 5A. Its for a DR9020 igniter I've put an LED in its place for now just to see if any current was flowing.

Below is the data sheet for the igniter it has a "all fire current" of 5A
http://webcache.googleusercontent.c...px?ResourceId=23162+&cd=1&hl=en&ct=clnk&gl=uk

 

Your link requires a log in.

I still need the igniter voltage when 5A is flowing through it?

 

Actually, now that I have seen the schematic, you need a voltage controlled switch, like an NMOS transistor. Presumably, you want current to flow through the igniter when the output pin of IC6b is high?

 

Yes thats exactly what I need

 

How would I wire one to get 5A through the igniter?

 

This is how I tried to do it http://imgur.com/XVHp6vL
I got more current but not enough

 

This is how I tried to do it http://imgur.com/XVHp6vL
I got more current but not enough

What NFET did you use?

Something wrong with your modified schematic. With 20V to the igniter, if it takes 5A, its internal effective resistance would be R=E/I=20/5=4Ω.

Your 1Ω would draw I=E/R=20/1=20Ω.

 

What NFET did you use?

Something wrong with your modified schematic. With 20V to the igniter, if it takes 5A, its internal effective resistance would be R=E/I=20/5=4Ω.

Your 1Ω would draw I=E/R=20/1=20Ω.

Mike I think you have a typo, should 20 ohms be 20 amps?

 

Looking at the data sheet for the DR9020 igniter the resistance is 0.65 - 0.9 ohms.
The typical all fire current is 5 amps. This could be more or less.
You need to remember the igniter is almost a dead short so most firing systems use drivers that can handle at least twice the current needed for all fire. Also igniters can short out after they are used so you should plan accordingly.

 

Mike I think you have a typo, should 20 ohms be 20 amps?

Yep. Sounds like you know more about igniters. Can you suggest a driver circuit that he can trigger from a 9V CMOS gate?

 

It just says its an ideal N type MOSFET.
Even if I remove the resistor I still get a smaller current than I need of 400mA which doesn't change even if I up the voltage.
http://imgur.com/MTOCrpZ

 

I guess this works http://imgur.com/agPKHGZ is there a better way to do this?