Field effect tetrode

The field effect tetrode is a solid-state device, constructed by creating two field effect channels back-to-back, with a junction between. It is a four terminal device with interesting properties. It does not have specific gate terminals since each channel is a gate for the other,[1] the voltage conditions modulating the current carried by the other channel.[2]

Current voltage relationship

Where the current in the first channel is , the current in the second channel is , the voltage of the first channel is - and in the second channel - we have:

and

Where the are the low-voltage conductance of the channels and is the pinch-off voltage (assumed to be the same for each channel).

Applications

The field effect tetrode can be used as a highly linear electronically variable resistor - resistance is not modulated by signal voltage. Signal voltage can exceed bias voltage, pinch-off voltage and junction breakdown voltage. The limit is dependent on dissipation. Signal current flows in inverse proportion to the channel resistances - signal does not modulate the depletion layer, meaning the tetrode can perform at high frequencies. The tuning ratio can be very large - the high resistance limit in the megohms range for symmetrical pinch off conditions.[1]

See also

References

  1. 1 2 Integrated circuits: Design Principles and Fabrication. Raymond M. Warner, Jr. and James N. Fordemwalt (editors). McGraw Hill. 1965. pp. 220–223.
  2. ↑ Academic Press Dictionary of Science and Technology. Christopher G. Morris (editor). Academic Press. 15 September 1992. p. 824. ISBN 9780122004001.

External links


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