I need to design a simple 20 mA current source, can any one tell me how do i do that

 

One fairly simple solution would be to design a current mirror.

Below is a link to the tutorial on this website that explains this technique using an simple example.

Current Mirror Tutorial

After reviewing the information in this tutorial you can then consider the things you need to decide on in addition to the 20ma current source value.

For example, what dc voltage do you have available to use in generating this current source

From your post, it seems safe to assume that you are just looking for a constant 20 ma source. Is this a safe assumption?

hgmjr

 

Current Mirror Tutorial

For example, what dc voltage do you have available to use in generating this current source

From your post, it seems safe to assume that you are just looking for a constant 20 ma source. Is this a safe assumption?

hgmjr

[post=16614]Quoted post[/post]​

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yes thats right, and the available voltage is 5 V dc.

 

Hi,

Get the spec sheet for an LM317 adjustable voltage regulator. It will show you a way to set it up as a current source.

 

Thanks !!