RF chip inductors are critical to many tuning and filtering circuits. Used in a variety of electronic systems, these essential circuit elements cut or eliminate electromagnetic-interference (EMI) noise on the printed-circuit board (PCB). They provide stable, low-loss inductance over broad frequencies in a small footprint, due to their monolithic construction. To impart some essential information on these components, Laird Technologies has published an application note titled, "RF Chip Inductor Applications."
The concise, five-page document covers three different kinds of chip inductors: multilayer, wire wound, and thin film. It lists their key parameters, such as inductance (L), DC resistance (DCR), rated current, quality factor (Q), and self-resonant frequency (SRF). The note examines SRF and Q in particular. SRF, for example, is the frequency at which the inductor and its inherent parasitic capacitance resonate. A higher SRF correlates with a higher effective operational frequency range for the inductor. The Q is a function of frequency; inductors with high Q perform better when it comes to narrowband-filtering, amplifier, and oscillator applications.
A table is provided to compare the features of the three types of chip inductors. Their four applications are listed as well: frequency filter, RF choke, oscillator, and impedance-matching circuits. The note concludes by pointing at the increased design of electronic systems with ever-slimmer profiles, such as cellular phones. Such products are making the implementation of small-form-factor, board-level, EMI-suppression components increasingly critical. In response to this trend, the note emphasizes that RF-chip-inductor monolithic construction provides stable, low-loss performance over broad frequencies. In a small footprintand in a ruggedized formsuch inductors can provide inductance tolerance at +10% of the specified frequency.
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