Cut-off (electronics)
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.
Cutoff values
Diodes
- Silicon diode: cutoff occurs when Vf falls below apx 0.6v. The exact voltage varies with temperature.
- Germanium diode: apx 0.3v, varying with temperature
- 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:
Transistors
- Silicon transistor: apx 0.6v, varying with temperature.
- Germanium transistor: apx 0.2v, varying with temperature
- BJT:
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.
See also
External links