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3-D view of the seven-terminal transformer

Modeling of the seven-terminal transformer implemented in the LTGC-QO

Minglin Ma, Yuan Chen, Xiangliang Jin, Zhijun Li, Chengwei Li, Xue Zhang


In this paper a seven-terminal transformer has been designed. We have suggested its equivalent-circuit model. This transformer has a primary coil with a center tap and two secondary coils. Based on this transformer, a low-cost transformer-based gate-coupled quadrature oscillator (LTGC-QO) using 0.18 μm CMOS technology has been developed. The LTGC-QO consumes 7 mW at 1 V power supply. The simulated phase noise at 1 MHz offset is –116.3 dBc/Hz. The chip area is 400×500 mm.


low cost device; transformer-based device; oscillator; quadrature oscillator

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