[SOLVED] Current Source from PWM input

[nitishn5]

Can someone suggest a circuit to convert 0-5V PWM voltage to DC current ranging from 0 to 500microamps.

It is for biomedical application so has to be precise enough(little drift, leakage)
Also the voltage developed should not be more than 40V. (The skin resistanse is assumed to be less than 100k )

 

[umesh49]

I assumed that you want variable current w.r.t. duty. You can first convert the signal to voltage by using a NPN transistor as switch with collector pulled up to supply with some 1k resistore and a low pass filter at collector output. Base can be driven by your PWM signal. Then convert the voltage (low pass filer output) to current by implementing a standard current source.