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The holding current (hypostatic) for electrical, electromagnetic, and electronic devices is the minimum current which must pass through a circuit in order for it to remain in the 'ON' state. The term can be applied to a single switch or to an entire device. A simple example of holding current is in a
The holding current (hypostatic) for electrical, electromagnetic, and electronic devices is the minimum current which must pass through a circuit in order for it to remain in the 'ON' state. The term can be applied to a single switch or to an entire device. A simple example of holding current is in a Spark gap
A spark gap consists of an arrangement of two conducting electrodes separated by a gap usually filled with a gas such as air, designed to allow an electric spark to pass between the conductors. When the potential difference between the conductor ...
.
In the most basic of circuits, if the current falls below the holding current even briefly, the circuit is turned 'OFF' (becomes blocked). However, complex circuits and devices may have different delays built-in between the time the current falls below this level and the time the device turns 'OFF'. Whether a device turns 'ON' when current is restored is a design issue. The current necessary to restore the circuit to the 'ON' state, called the "threshold current" (See threshold voltage
The threshold voltage, commonly abbreviated as Vth or VGS(th), of a field-effect transistor (FET) is the minimum gate-to-source voltage (VGS) that is needed to create a conducting path between the source and drain terminals. It is an important s ...
), may be much greater than the holding current, or only very slightly more. Nevertheless, where the device is designed to turn back 'ON' upon restoration of the current and where the device is running at or about the holding current level, slight variations in the current can cause ''flicker'' as the device cycles 'OFF' and 'ON'. If flicker is undesirable, it can be reduced by the use of capacitors or other circuits, on the other hand, flicker can be used to measure small events as in a Geiger–Müller tube
The Geiger–Müller tube or G–M tube is the sensing element of the Geiger counter instrument used for the detection of ionizing radiation. It is named after Hans Geiger, who invented the principle in 1908, and Walther Müller, who collaborated w ...
.
A related term is latching current, which is the minimum additional current that can make up for any missing input (gate) current in order to keep the device 'ON', in other words, to keep the device's internal structure latched.
See also
*Silicon controlled rectifier
A silicon controlled rectifier or semiconductor controlled rectifier is a four-layer solid-state current-controlling device. The name "silicon controlled rectifier" is General Electric's trade name for a type of thyristor. The principle of four ...
(SCR), a device for maintaining a holding current
*Thyristor
A thyristor () is a solid-state semiconductor device with four layers of alternating P- and N-type materials used for high-power applications. It acts exclusively as a bistable switch (or a latch), conducting when the gate receives a current ...
, a device for maintaining a holding current
*TRIAC
A TRIAC (triode for alternating current; also bidirectional triode thyristor or bilateral triode thyristor) is a three terminal electronic component that conducts current in either direction when triggered. The term TRIAC is a genericised tradem ...
, a device that can conduct current in either direction when it is turned on
Notes
{{- Solid state switches Power electronics