I am trying to build a linear gain voltage controlled amplifier using an N-channel JFET as a voltage variable resistor (see circuit below).
As the circuit is set op now, I would expect Vout to be zero since the negative input of the opamp is grounded.
But what I find instead is that Vout depends linearly on the gate voltage Vgate above some threshold (Vgate = 0.6V).
Why does Vout depend on Vgate for this particular circuit?
simulate this circuit – Schematic created using CircuitLab