Integrator with JFET (CB6229E)

This circuit was found in an 80s National Semiconductor documentation. The configuration holds true for modern JFETs.

1 V Phone Amplifier (CB15563E)
Using a new Maxim integrated circuit (www.maxim-ic.com) the amplifier shown in the figure can be...
FET Electrometer (CB13661E)
We found this circuit of extreme sensitivity in a 1974 documentation. The circuit can be assembled with...
Amplifier stage (CB21940E)
This circuit with germanium transistors was found in a publication by Gernsback from 1960. The...