Q & A

1.

How to define 'direct resistance (Rdc)'?

Ans:

The resistance caused by direct current flowing through a coil. While a coil has higher resistance that means the coil makes higher power loss, then service life of the battery will be shorter. Therefore, if designing the resonant circuits or impedance matching circuits, lower direct resistance of coil is desirable.

2.

How to define the quality factor (Q) of thin film Inductor?

Ans:

For an inductor, only the energy stored in the magnetic field is of interest. Any energy stored in the inductor!|s electric field, because of some inevitable parasitic capacitance in a real inductor, is a loss. Therefore, the efficiency of an inductor is measured by its Q, which is limited by the parasitic. Hence, Q is proportional to the net magnetic energy stored, which is equal to the difference between the peak magnetic and electric energies.

3.

How an inductor could 'self-resonant' at a certain frequency?

Ans:

Normally, we call that certain frequency as Self-Resonant Frequency, namely, SRF. A self-resonant occurs on an inductor because of its parasitic capacitance which the peak electric energy stored in electric field equals to the peak magnetic energy stored in magnetic field. So, an inductor will not work if it is over the self-resonant frequency (SRF). Hence, for designing resonant circuits or impedance matching circuits, higher frequency than the operating frequency is required and desirable.

4.

How to define allowable direct current (Idc)?

Ans:

The allowable amount of direct current flows through an inductor without any deterioration. Thus, if a current over the allowable current flows, excessive heat will be generated and the quality will be degraded.

5.

Operating temperature range?

Ans:

The allowable range of the environmental temperature that is around a coil to keep an inductor working optimally. However, it does not contain the naturally generated heat. Thus, for designing resonant circuits or impedance matching circuits, it has to fit the operating temperature range of the set.