I have a simple Wien Bridge Oscillator (with JFET gain control) circuit pictured below. This circuit works as expected at lower voltages (+/-9 V), but I am running into some problems with higher voltage supplies (+/-16 V). I believe the JFET (2N3819) is burning out early in operation from some kind of transient voltage spike.
I have a supply voltage of 32 volts DC, which is then split with a virtual ground Op Amp circuit to create the +/- 16 V. From the schematic, I thought that the 25 V JFET should be fine since the greatest possible potential over it would be only 16 V. Is there an effect that might cause that transistor to exceed that voltage, or am I missing something here? Perhaps the voltage splitter allows this kind of transient?
Unfortunately, I do not have the equipment to test and record the time history of the circuit to verify the problem. I have successfully simulated the circuit in LTSpice, where the max potential developed at the gate of the JFET is within only -3 V.
If the problem is indeed with the JFET at higher voltages, what JFET might perform similarly at higher voltages? By similarly, I mean a resistance profile that allows for gain control in the Wien Bridge Oscillator.