Cut-off (electronics)
Encyclopedia
In electronics, the term Cut-off identifies a state of negligible
electrical conduction which is proper of several types of electronic component
s 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.
Negligible
Negligible refers to the quantities so small that they can be ignored when studying the larger effect. Although related to the more mathematical concepts of infinitesimal, the idea of negligibility is particularly useful in practical disciplines like physics, chemistry, mechanical and electronic...
electrical conduction which is proper of several types of electronic component
Electronic component
An electronic component is a basic electronic element and may be available in a discrete form having two or more electrical terminals . These are intended to be connected together, usually by soldering to a printed circuit board, in order to create an electronic circuit with a particular function...
s when a control parameter (which usually is a well-defined voltage
Voltage
Voltage, otherwise known as electrical potential difference or electric tension is the difference in electric potential between two points — or the difference in electric potential energy per unit charge between two points...
or electric current
Electric current
Electric current is a flow of electric charge through a medium.This charge is typically carried by moving electrons in a conductor such as wire...
, but could also be an incident light intensity
Intensity (physics)
In physics, intensity is a measure of the energy flux, averaged over the period of the wave. The word "intensity" here is not synonymous with "strength", "amplitude", or "level", as it sometimes is in colloquial speech...
or a magnetic field
Magnetic field
A magnetic field is a mathematical description of the magnetic influence of electric currents and magnetic materials. The magnetic field at any given point is specified by both a direction and a magnitude ; as such it is a vector field.Technically, a magnetic field is a pseudo vector;...
), 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
Electronic component
An electronic component is a basic electronic element and may be available in a discrete form having two or more electrical terminals . These are intended to be connected together, usually by soldering to a printed circuit board, in order to create an electronic circuit with a particular function...
considered, and also the speed
Speed
In kinematics, the speed of an object is the magnitude of its velocity ; it is thus a scalar quantity. The average speed of an object in an interval of time is the distance traveled by the object divided by the duration of the interval; the instantaneous speed is the limit of the average speed as...
of this transition varies considerably.
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:
- MOSFET:
- Triac:
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
- DiodeDiodeIn electronics, a diode is a type of two-terminal electronic component with a nonlinear current–voltage characteristic. A semiconductor diode, the most common type today, is a crystalline piece of semiconductor material connected to two electrical terminals...
- Electrical conduction
- Electronic componentElectronic componentAn electronic component is a basic electronic element and may be available in a discrete form having two or more electrical terminals . These are intended to be connected together, usually by soldering to a printed circuit board, in order to create an electronic circuit with a particular function...
- Field effect transistor in JFETJFETThe junction gate field-effect transistor is the simplest type of field-effect transistor. It can be used as an electronically-controlled switch or as a voltage-controlled resistance. Electric charge flows through a semiconducting channel between "source" and "drain" terminals...
and MOSFETMOSFETThe metal–oxide–semiconductor field-effect transistor is a transistor used for amplifying or switching electronic signals. The basic principle of this kind of transistor was first patented by Julius Edgar Lilienfeld in 1925...
form - TransistorTransistorA transistor is a semiconductor device used to amplify and switch electronic signals and power. It is composed of a semiconductor material with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's terminals changes the current...
- Vacuum tubeVacuum tubeIn electronics, a vacuum tube, electron tube , or thermionic valve , reduced to simply "tube" or "valve" in everyday parlance, is a device that relies on the flow of electric current through a vacuum...