In a JFET SELE transistor, there is no voltage source to feed the circuit, from where is the circuit fed with reverse or negative voltage in order for the circuit to work, I need the answer in theory...

In a JFET SELE transistor, there is no voltage source to feed the circuit, from where is the circuit fed with reverse or negative voltage in order for the circuit to work, I need the answer in theory only in a clear, simple and understandable line. Thank you ?

Extracted text: In a JFET SELE transistor, there is no voltage source to feed the circuit, from where is the circuit fed with reverse or negative voltage in order for the circuit to work, I need the answer in theory only in a clear, simple and understandable line. Thank you