Designing a variable current source

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Hey!
I want to design a variable current source, voltage controlled - from 0.1mA to 2.5A.
Do you have any tips, circuits, etc?

Many thanks!
 

What voltage, high side or low side? A diagram of exactly what you want would help.

Just google 'current source' and you'll see many topologies.
 

Hi,

this already has been discussed many times.
You will find many threads here in the forum and many more in the internet.
Simplest: click on the links in the box below "similar threads".

Btw: I agree with the posts above. Missing a lot of your requirements / specifications.

Klaus
 

Hey all!
Thanks for replying.
I'm currently working on specification.
All I know for now is that the control voltage should be 0-5V OR 0-10V, preferably to 0-5V.
About a block diagram- attached


Klaus, What does it mean high side or low side?

Thanks again. I will try and go through similar posts and come back if I'll have any more questions
 


Hi,
Thanks for clarifying.
I looked on your tutorial and tried simulating it at LTSPICE and didn't get any results.
I'm still reading about it in various sources.
The things I see the most are an OPAMP in which the output is connected to a transistor (BJT or MOS) that opens the current for the load.
How do I begin in designing a one of my own? How do I chose the opamp, the type of transistor, etc?


The requirements I have so far:
- Controlled current- between 0.1mA to 2.5A
- Controlling voltage- 0-5V
- No frequency response as far as I know
- About high/low side- I will read about it more in order to figure out what is best for the design.

Thanks again.
 

Hi,

How do I begin in designing a one of my own? How do I chose the opamp, the type of transistor, etc?
Click to expand...
There is a tutorial.. and you ask how to start.
...Maybe start telling us what you did so far and what results you get. Informations like "didn't get any results" aren´t helpful..

How do I chose the opamp, the type of transistor, etc?
Click to expand...
OPAMP:
Uncritical. Use a common one for the simulation. If the simulation fails it won´t burn down your house. That´s the benefit of a simulation.
For real world: Power supply should meet your requirements... That´s the most critical.

Transistor:
.... is written in the tutorial.

Klaus
 

Here's a common, low-side, constant-current circuit consisting of an N-MOSFET and an opamp.
The op amp must be a single-supply type, and the MOSFET should be rated for at least 5A.
The MOSFET must be mounted on a heatsink.
R1 should be a 1W resistor.
The circuit values shown give a current of 0-2.5A for a 0-5V input.
 

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Hey
Here is the simulation I ran:


The graph is the Iload vs V1 (Input)

I think the problem is with the transistor and OPAMP I chose? I will try to simulate again. Thanks!

31crutschow, Thanks. I will try it as well.
 

Hi,

you missed to add the 40k resistor between R5 and R6..

Klaus
 

Hey everyone
For the meantime we decided to try the solution summitville offered, a dedicated IC: LT3083 & LT3086.
I will update in any changes or progress I will make in them or in the other circuits.
Thanks for the help!
 

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