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Constant current source adjustable by PWM

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delphes123:
Dear

I would like to get Constant current source, but the level of current needs to be adjustable (from 0 to 20 MA approx), I need to have very low cost of BOM, best is to avoid OP Amps if possible.

R3 is the charge where I need constant current.

The idea is to replace V2 source by MCU PWM output

How this schematic could be improved? Does Q2 needs to be replaced by Mosfet ?

Thanks

paulca:
20MA ... that's a lot of current!  I assume you mean "mA".

schmitt trigger:
Why are you against using an opamp? Why are you restricting the use of a component which will make your life easier and performance better?

delphes123:
Yes sorry typo is mA of course

delphes123:
Not using OP Amps is mainly cost problem with this project, but if there are no solutions why not ?

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