Cut-off (electronics)
In electronics, cut-off is a state of negligible conduction that is a property of several types of electronic components when a control parameter, is lowered or increased past a value. 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
- Copper oxide diode: Usually between germanium and silicon diodes
- Diac: Depends on configuration.
- Germanium diode:apx 0.3 V; varying with temperature.
- Schottky diode:0.10–0.45, varying with temperature.
- Selenium diode:Depends on age and current. Usually higher than silicon diodes.
- Silicon diode: cutoff occurs when Vf falls below apx 0.7 V. The exact voltage varies with temperature.
- Thermionic diode: cutoff voltage depends on device design. Much higher than for silicon devices.
- Zener diode: reverse cutoff defined by diode voltage rating. Forward cutoff apx 0.6 V.
Transistors
- BJT: Depends on the configuration.
- Germanium transistor: apx 0.2 V, varying with temperature.
- MOSFET: Depends on the configuration.
- Silicon transistor: apx 0.6 V, varying with temperature.
- TRIAC: Also depends on the configuration.
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.