How to choose a suitable capacitor -
How to choose a suitable capacitor -
This paper mainly introduces how to choose a suitable capacitor, this article word count 1200 words, read the full article 12 minutes.
Capacitor correctly choose 1, select the appropriate model usually used in low frequency coupling, bypass decoupling in the circuit, such as electrical performance requirements are not strict with paper capacitor, electrolytic capacitor, etc.
Coupling capacitor of low frequency amplifier, choose 1 -
22 u F electrolytic capacitor.
Bypass capacitor is selected according to the circuit operating frequency, as in the low frequency circuits, launch the bypass capacitor choose electrolytic capacitor, capacity between 10 ~ 220 u F, can choose 0 in the intermediate frequency circuit.
01 ~ 0.
1 u F paper, film capacitor etc;
In the high frequency circuit, should choose mica capacitor and ceramic capacitor.
In the power supply filter and decoupling circuit, can choose electrolytic capacitor.
On these occasions, the demands of capacitor is not high, as long as allow volume, capacity is enough.
2, the rational selection of precision in the bypass capacitor, decoupling, low frequency coupling circuit, if the accuracy is not very strict requirements for capacitors, when use, can according to the design value, choose similar or slightly larger capacity of the capacitor.
But in other circuits, such as the control circuit of the oscillation circuit, delay circuit, tone, the capacity of the capacitor will need to be as much as possible and the calculated value is consistent.
Among various kinds of filter, the precision of electric capacity have higher requirements, should choose the high accuracy of capacitor.
3, determine the rated working voltage of capacitor rated working voltage of capacitor voltage should be higher than the actual work, and have enough cushion, in case of damage caused by the voltage fluctuation.
In general, should make the working voltage is lower than 10% ~ 20% of the rated working voltage of capacitor.
In some circuit, voltage fluctuation is bigger, can have a bigger margin.
Generally small capacity capacitor dielectric loss is small, heat resistance performance and stability are good, but the circuit requirement for them is often is higher, so when choosing the rated working voltage should still have a certain margin, also want to pay attention to the influence of the temperature of working environment.
4, try to choose large capacitor insulation resistance insulation resistance the smaller the capacitor, the greater the leakage current, the leakage current is not only the loss of power in a circuit, the important is that it can lead to circuit work properly or degrade the performance of the circuit.
Leakage current of power loss, can make the condenser heat, and its temperature, and will produce larger leakage current, so cycle, easy to damage the capacitor.
When choosing a capacitor, therefore, should choose the capacitor insulation resistance is high enough, especially under the condition of high temperature and high pressure using capacitor, 5, and consider the temperature coefficient and frequency characteristic of capacitor temperature coefficient is larger, the capacity along with the change of temperature, the greater the it in many circuits are not allowed.
Such as oscillation circuit elements in the oscillation circuit, phase shift network components, such as filter, temperature coefficient is big, can make the circuit produces drift, destabilize the circuit work.
These occasions should choose small temperature coefficient of capacitor, to make sure it can work stable.
6, pay attention to use the environment using the environment is good or bad, directly affects the performance and life of capacitor.
In the environment of the working temperature is higher, capacitor is prone to leakage and accelerated aging.
So in the design and installation, because as far as possible use small temperature coefficient of condenser, and away from heat source and improve the internal ventilation cooling, when necessary, should be forced air cooling.
In cold conditions, because the temperature is very low, normal electrolytic capacitor failure due to the electrolyte is icy, make the equipment work properly, so must use hardy electrolytic capacitor.
Under the condition of multiple sand or work in humidity larger environment, should choose sealed type capacitor, dustproof wave resistance in order to improve the equipment.
HTML this paper label: a capacitance capacitor: why SMT components used in the circuit board now than plug-in components next article: monolithic capacitor has the branch is negative?