Cut-off (electronics)

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In electronics, the term Cut-off identifies a state of negligible electrical conduction which is proper of several types of electronic components when a control parameter (which usually is a well defined voltage or electric current, but could also be an incident light intensity or a magnetic field), is lowered or increased past a value called conduction threshold or simply threshold. The transition from normal conduction to cut-off can be more or less sharp, depending on the type of device considered, and also the speed of this transition varies considerably.

1 Cutoff values
2 See also

[edit] Cutoff values

[edit] Diodes

Silicon diode: cutoff occurs when Vf falls below apx 0.6v. The exact voltage varies with temperature.
Germanium diode:
Schottky diode:
Diac:
Zener diode: reverse cutoff defined by diode voltage rating. Forward cutoff apx 0.6v.
Thermionic diode: cutoff voltage depends on device design. Much higher than for silicon devices.
Copper oxide diode:
Selenium diode:

[edit] Transistors

Silicon transistor: apx 0.6v, varying with temperature.
Germanium transistor: apx 0.2v, varying with temperature
BJT:

MOSFET:
Triac:

lancau

[edit] Valves

Triodes: triodes cut off when applied grid bias is too low. This will be a negative voltage under ordinary conditions.
Tetrode, Pentode etc: There is some degree of interaction between the grids, and values will vary from one device to another. Anode voltage also affects cutoff voltage.