Novel differential inductor design for high self-resonance frequency

Symmetric inductors which exhibit constructive inductive coupling between inter-twined halves (branches) under differential drive (i.e., differential inductors) are widely used in differential circuits in place of two separate, single-ended inductors when high Q is required and/or when space is at a premium. One disadvantage of such a differential inductor is the strong capacitive coupling between the two branches causing a low self-resonance frequency (F/sub SR/) when compared to two separate, nominally uncoupled inductors for the same application. This paper presents a novel layout design for differential inductors that largely mitigates this effect, thus extending the usable frequency range.