Gunn diode
![A Russian-made Gunn diode](/Images/godic/202502/17/Ganna_diode_3A703B1935.jpg")
![Current-voltage (IV) curve of a Gunn diode. It shows negative resistance above the threshold voltage (Vпорог)](/Images/godic/202502/17/Diod_gunn1935.jpg")
![Russian Gunn diode oscillator. The diode is mounted inside the cavity (metal box), which functions as a resonator to determine the frequency. The negative resistance of the diode excites microwave oscillations in the cavity which radiate out the hole into a waveguide (not shown). The frequency can be adjusted by changing the size of the cavity using the thumbscrew.](/Images/godic/202502/17/Ganna_gjenerators_M31102-11935.jpg")
![Disassembled radar speed gun. The grey assembly attached to the end of the copper-colored horn antenna is the Gunn diode oscillator which generates the microwaves.](/Images/godic/202502/17/Radar_speed_gun_internal_works1935.jpg")
A Gunn diode, also known as a transferred electron device (TED), is a form of diode, a two-terminal passive semiconductor electronic component, with negative resistance, used in high-frequency electronics. It is based on the "Gunn effect" discovered in 1962 by physicist J. B. Gunn. Its largest use is in electronic oscillators to generate microwaves, in applications such as radar speed guns and microwave relay data link transmitters.