1. Size of inductance.0402,0603, etc., should pay attention to is the centimeter mark, or inch mark, inductance size mark each company is not consistent, murata company sometimes one way of marking, sometimes two ways of marking.Unless otherwise stated, it generally refers to inch mark.
2. Inductance.The basic parameter of inductance is the quantity of inductance. The main units are: Henry (H), hau Henry (mH), micro Henry (uH),
The relationship between them:
1 h = 1000 mh = 1000000 uh
3. Rated current of inductance.There are two types: one is the rated current according to the change of inductance value (sensitivity change of 30%), the rated current according to the increase of inductance temperature (inductance increase of 40 degrees or less, the final temperature is below 125 degrees Celsius).Sometimes only one is given, indicating that the other rated current is not the limiting factor.
In addition to these, understand the use of customer inductance, the role of the use of inductance, inductance structure is necessary, otherwise the material may not be accurate.
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4. Sometimes there are certain requirements on the sensitivity error.
5. Dc resistance
6. Self-resonant frequency
Inductance burden is more complex, according to the different structure, can be divided into winding line, laminated type and thin film type, according to the different adaptive circuit can be divided into above 100MHz rf, 100MHz below general use, power line.The product adaptation of each classification method overlaps.
LQH (coil ferromagnetic core, choke, electromagnetic shield choke) series or LQM (laminated ferromagnetic core, dc power choke) series are recommended for power line and general circuit, mainly used for voltage conversion, choke, resonant circuit and general filter circuit.
Rf inductance recommended LQW_H LQH_H series (winding linear ferromagnetic core), LQW_A series (winding linear non-magnetic material), LQG series (laminated non-magnetic material), LQP series (thin film non-magnetic material), mainly used for impedance matching, high-frequency filter circuit, rf choke.
The characteristics of rf inductors for winding radio frequencies are high Q and high sensitivity.The main characteristic of if wound rf inductor is high Q.The main characteristics of laminated rf inductors are designed according to industry standards.The main characteristics of thin film rf inductor are small size and high Q value.
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SRF: Resonant Frequency
1. When the frequency is lower than the self-resonant frequency (SRF), the inductive reactance increases with the frequency;
2. When the frequency is equal to the self-resonant frequency (SRF), the inductive reactance reaches the maximum value;
3. When the frequency is higher than the self-resonant frequency (SRF), the inductive reactance decreases with the increase of frequency;
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Inductance application scenarios
1. When the inductor is used as the choke inductor (choke coil/choke) (such as the dc supply inductor at the output end of the rf amplifier), the highest frequency of the signal should be at the self-resonant frequency of the inductor. Considering the inductance error, the self-resonant frequency of the inductor should be slightly higher than the highest frequency of the signal.
2.Other applications (filter and matching) : inductance should be as constant as possible within the signal bandwidth. Therefore, the inductance's self-resonant frequency (SRF) should be 10 times the maximum frequency of the signal (the empirical value recommended by CoilCraft).
The relationship between inductance and self-resonance frequency (SRF)
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Typically, the higher the inductance, the lower the self-resonant frequency (SRF), and vice versa, because of the inductance's parasitic inductance.
Post time: Oct-22-2019