How could I proceed in selecting a filtering circuit for a DC circuit being measured?
I have a 5pF capacitor being sensed by a jfet (i.e.-2n5459 gen.purp.); meaning the high impedance gate-source is parallel to the capacitor and its Rdischarge. Right now, 1.5kohm is jfet's Rs and is the input load/Rgen to a DC differential amplifier, meant to amplify the tiny DC fluctuations on the capacitor.
I don't want to have a parallel capacitor filter the DC fluctations nor do I want a series inductor too either. Possibly 60Hz, or better yet 6Hz, should be eliminated from the DC measurement signal.
Is there something I'm missing? A compromising point to reconcile with? Please fill me in!
I have a 5pF capacitor being sensed by a jfet (i.e.-2n5459 gen.purp.); meaning the high impedance gate-source is parallel to the capacitor and its Rdischarge. Right now, 1.5kohm is jfet's Rs and is the input load/Rgen to a DC differential amplifier, meant to amplify the tiny DC fluctuations on the capacitor.
I don't want to have a parallel capacitor filter the DC fluctations nor do I want a series inductor too either. Possibly 60Hz, or better yet 6Hz, should be eliminated from the DC measurement signal.
Is there something I'm missing? A compromising point to reconcile with? Please fill me in!