What is varistor diode?
A varistor is an electronic component with an electrical resistance that varies with the applied voltage. Also known as a voltage-dependent resistor (VDR), it has a nonlinear, non-ohmic current–voltage characteristic that is similar to that of a diode. The name varistor is a portmanteau of varying resistor.
What is the difference between diode and varistor?
The ability to protect sensitive circuit parts from high transient voltages is the same function a TVS diode provides. Varistors are bidirectional components suitable for both AC and DC circuits. They come in different design packages.
Is varistor a semiconductor?
Definition: A varistor is a 2 terminal semiconductor device that protects the electrical and electronic devices from overvoltage transients. Its resistance is dependent on the applied input voltage.
What is the difference between fuse and varistor?
Unlike the fuse or circuit breaker which offers over-current protection, the varistor provides over-voltage protection by means of voltage-clamping in a similar way to the zener diode. In many ways the varistor looks similar in size and design to a capacitor and is often confused as being one.
What is varistor used for?
Varistors are used to protect a circuit from high voltage surges. When a high voltage surge is applied to a circuit, the outcome is usually catastrophic to the circuit. A capacitor may be installed across the signal lines. However, this capacitor cannot suppress voltage surges.
How is varistor measured?
How do you test for varistor? Touch one meter probe to the free varistor lead and the other probe to the connected lead. Read the resistance on the meter. If it reads nearly infinite resistance, the varistor is still good.
Do varistors have polarity?
Does a varistor have polarity? In the case of metal oxide varistor, a zinc-oxide layer is basically sandwiched between two metal electrodes. As a result, there is no polarity.
Is varistor a resistor?
A varistor is a voltage dependent resistor (VDR). The resistance of a varistor is variable and depends on the voltage applied. The word is composed of parts of the words “variable resistor”.
Does a varistor have polarity?
Metal Oxide Varistors are similar to resistors and has only two leads. There is no polarity for these leads and hence can be connected in both directions.
Do varistors go bad?
Most surge protectors contain MOVs (Metal Oxide Varistors). After enough events, the MOV will fail and leave you with no protection. But an MOV can fail catastrophically if there is no current-limiting fuse in series with it. And if a current-limiting fuse blows, it will let a serious voltage peak go undamped.
How do you check if a varistor is working?
Touch one meter probe to the free varistor lead and the other probe to the connected lead. Read the resistance on the meter. If it reads nearly infinite resistance, the varistor is still good. If it reads very low resistance, the varistor is blown.
How are diodes connected in a metal oxide varistor?
In a metal oxide varistor, the two immediate neighbouring zinc grains will form a diode junction between their borders. Hence a metal oxide varistor can be considered as a collection of huge number of diodes that are connected in parallel.
How is a varistor used in a circuit?
A varistor is one such type of resistor, used to change the resistance in the circuit by changing the voltage. Its design is almost similar to that of a capacitor. These are generally of two types which are metal oxide and silicon carbide.
What kind of metal is a varistor made of?
Usually, zinc oxide is used in its manufacturing thus is also known as metal oxide varistor. The figure below shows the structure of metal oxide varistor: Here the varistor is formed 90% with zinc oxide and the rest is filler material that forms the junction.
How to design a circuit using a varactor diode?
For designing circuits that use the properties of a varactor diode, we first need to break down its electrical properties and visualize an equivalent circuit with basic components like resistors, capacitors and inductors. The below image shows such approximate equivalent circuit of a varactor diode when operated under reverse bias condition.