user31568: I need programmable current control, fading from zero to 2 milliAmps.  I was hoping to use Arduino's AnalogWrite(), which uses Phase Width Modulation (PWM) to simulate analog output with a sawtooth wave on a duty-cycle; to control an LM334Z to deliver a slowly ramped low current delivery.
[The application is a TransCranial Direct Current Stimulation (TDCS) micro-current delivery to the human scalp. Jumping straight to 2 milliAmps is uncomfortable].
Will PWM work? Or, do I need some sort of smoothing circuitry to soften the PMW before it is applied to the LM334Z's Rset pin to accomplish the above?

user35212: If you don't need super high accuracy, using a MOSFET's ohmic region, plus a smoothing filter on the output of your PWM (analog out), could be a solution.  

31568: <p>I need programmable current control, fading from zero to 2 milliAmps.  I was hoping to use Arduino's AnalogWrite(), which uses Phase Width Modulation (PWM) to simulate analog output with a sawtooth wave on a duty-cycle; to control an LM334Z to deliver a slowly ramped low current delivery.
[The application is a TransCranial Direct Current Stimulation (TDCS) micro-current delivery to the human scalp. Jumping straight to 2 milliAmps is uncomfortable].
Will PWM work? Or, do I need some sort of smoothing circuitry to soften the PMW before it is applied to the LM334Z's Rset pin to accomplish the above?</p>
 35212: <p>If you don't need super high accuracy, using a MOSFET's ohmic region, plus a smoothing filter on the output of your PWM (analog out), could be a solution.  </p>
