Can someone please explain the purpose of using the JFET in the configuration attached in the image? I understand the JFETs are for amplification purpose but I am unable to understand the working of JFETs in below configuration. Gate of the second JFET is given to the input of OP-AMP. The OP-AMP here is being used as a buffer. The input to first JFET would be AC signals in the range of 1uV to 200uV (Brain waves). The output of OP-AMP is then connected to Instrumentation amplifier followed by high precision ADC.
Also, a resistor is being connected at the non inverting terminal of the OP-AMP and is connected to an external voltage source. Due to the P.D, there will be a current flow as shown in the image and the current will flow to the Drain of first JFET. Is it possible? If yes, please let me know.
Any readable resource will be highly appreciated.