gunn diode modes

Discussion in 'General Electronics Chat' started by bharathig_8, Nov 10, 2006.

  1. bharathig_8

    Thread Starter New Member

    Nov 10, 2006
    i do not get the concept of how domains are formedin the gunn diode
  2. Dave

    Retired Moderator

    Nov 17, 2003
    Moved to the General Electronics Chat where this is better suited.

  3. bharathig_8

    Thread Starter New Member

    Nov 10, 2006
    can i ask my doubts related to microwave circuits and devices
  4. mrmeval

    AAC Fanatic!

    Jun 30, 2006

    The operation of the Gunn diode can be explained in basic terms. When a voltage is placed across the device, most of the voltage appears across the inner active region. As this is particularly thin this means that the voltage gradient that exists in this region is exceedingly high.

    It is found that when the voltage across the active region reaches a certain point a current is initiated and travels across the active region. During the time when the current pulse is moving across the active region the potential gradient falls preventing any further pulses from forming. Only when the pulse has reached the far side of the active region will the potential gradient rise, allowing the next pulse to be created.

    It can be seen that the time taken for the current pulse to traverse the active region largely determines the rate at which current pulses are generated, and hence it determines the frequency of operation.

    A clue to the reason for this unusual action can be seen if the voltage and current curves are plotted for a normal diode and a Gunn diode. For a normal diode the current increases with voltage, although the relationship is not linear. On the other hand the current for a Gunn diode starts to increase, and once a certain voltage has been reached, it starts to fall before rising again. The region where it falls is known as a negative resistance region, and this is the reason why it oscillates.
  5. beenthere

    Retired Moderator

    Apr 20, 2004

    Are those doubts related to the existence of microwave circuits and devices, or something else? Specificity helps.