Inductor Guide

Basic Facts about Inductors [Lesson 4] Roles of Inductors - "Structure of inductors"

The basics of inductors are explained in this technical column.
The topic dealt with in Lesson 4 describes the structure of inductors.

[Lesson 4] Roles of Inductors ‐Structure of inductors‐

Lessons 2 and 3 dealt with high-frequency inductors and power supply line inductors.  In this lesson we will look at the differences in the characteristics of inductors and their uses and applications from the perspective of their structures.
  Wire wound, multilayer and film are the main structures used by Murata's inductors.  This lesson examines what are the differences in characteristics based on the structures of Murata's high-frequency inductors and how inductors with each of these structures are used.

The frequency characteristics of the Q are shown in the graph by structure (wire wound, multilayer) of Murata's high frequency coil 1005 size. As shown in Figure 1, the feature of the wire wound type is the very high Q factor compared with the multilayer type.
The feature of the film type is also the Q factor that is higher than the multilayer method which is adopted by other companies in the same industry. Murata offers the film type in the small 0603 size and the 0402 size. (Figure 2)

Figure 1: Comparison of Q Characteristics between Multilayer LQG15 Series and Wire Wound LQW15 Series (both 2.7 nH)
Figure 2: Comparison of Q Characteristics between 0603 Size, LQP03TN Series and Multilayer Products of Other Companies (both 10 nH)

Next, we look at the uses and applications of high-frequency coils by structure.  High-frequency coils are mainly used in cell phones, wireless LANs and other high-frequency circuits.  Some typical examples of their uses and applications are described below.

The wire wound inductors in the LQW series feature a high Q value.  Inductors with high Q values are used in the matching circuits of RF units because their high Q values give them excellent attenuation characteristics inside the pass band of the filters.  They are also frequently used in the matching applications of antennas for maintaining the transmission and reception sensitivity of the antennas.  Furthermore, since they have low Rdc characteristics, they are also employed in choke circuits in which high current levels flow.

The film inductors in the LQP series have a different set of features, since micromachining of the coil patterns is enabled by forming the electrodes using a photolithography technique.  The inductors can have smaller sizes and high Q characteristics, while at the same time the series offers a line-up of inductors with inductance values that both deviate minimally and are finely graded.  The line-up consists of a wide range of the inductors in the 0603 size, which is becoming the mainstream, and in the 0402 size, which is the smallest in the industry, and both sizes support the trend toward miniaturized sizes.  These inductors are used in the matching and resonance circuits of RF units that require miniaturized sizes, minimal deviation in inductance and finely graded inductance levels.  They are also used in choke circuits that demand miniaturized sizes and low Rdc.

Multilayer inductors have the lowest Q value of the three structures.  They feature a good overall balance in terms of the inductance value line-up, size and cost, and are used in the matching and resonance circuits of RF units and in all kinds of choke circuits.

Each of the three structures has its own special features, and each should be used in ways that capitalize on those special features.  In the next lesson, we will look at inductor mounting.


person in charge: Murata Manufacturing Co., Ltd. S.S

The information presented in this article was current as of the date of publication. Please note that it may differ from the latest information.

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