A linear integrated LC bandpass filter with Q-enhancement

A technique is proposed in this paper for linearizing active Q-enhanced monolithic LC filters. This technique employs capacitive dividers and tunable linear transconductors. Various multi-tanh translinear circuits ran be used to implement the linear transconductors, taking into consideration the need for linear operating range and the low supply voltage. A linear Q-enhanced LC filter using the proposed technique has been implemented in a 0.5-mu m bipolar process. The demonstrated filter chip operates at a center frequency around 1 GHz with the quality factor tunable up to 400 without spurious oscillation. For a Q of 40, the input intercept point and spurious-free dynamic range are -6.67 dBm and 36 dB, respectively, at a power consumption of 68 mW and with 7 dB of gain.