Noise in current source

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Hello,

I continue my experimentation on a preamplifier and am working now on the current source. I'm trying to make it adjustable. I've tried zener diodes or leds with paralleled trim pot to drive the mosfet's gate, seems to be noisy. Now I've attached a jfet 2SK30 in current source configuration feeding a trim pot and it's quieter but it stay little noise.

Do you think the trim pot could be responsable, and is a winding pot quieter???

Thanks
 
hugobors said:
Hello,

I continue my experimentation on a preamplifier and am working now on the current source. I'm trying to make it adjustable. I've tried zener diodes or leds with paralleled trim pot to drive the mosfet's gate, seems to be noisy. Now I've attached a jfet 2SK30 in current source configuration feeding a trim pot and it's quieter but it stay little noise.

Do you think the trim pot could be responsable, and is a winding pot quieter???

Thanks


If I understand you correctly (schematic please!) that you vary the ref with a pot to the gate, why not filter the reference going to the gate with an R-C? That'l take care of most of the noise.

Jan Didden
 
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