In order to see the large signal negative resistance of the JFET oscillator experimentally, the output impedance including the negative resistance of the oscillator is measured at the out-put port by eliminating the load and connecting a source and the impedance meter through a circulator which is designed and built by using two operational amplifiers at the oscillating frequency of 890KHZ. The measured negative resistance stays almost constant (about-390 ohm) in the region of small singal but its absolute value decreases and becomes positive resistance as the signal strength increases. Output resistance stays capacitive in the small signal region but becomes inductive in the large signal region.
