Novel linearization circuit for BiCMOS transconductors used in high frequency OTA-C filters

A novel linearization circuit for a tunable BiCMOS transconductor based on the emitter degeneration of bipolar devices is analyzed. The transconductor is suitable for high-frequency continuous-time filter implementations because of the large value of the gm/I ratio and its ease of tunability. An integrator cell with a unity gain bandwidth of up to 80 MHz can be realized with a capacitive load as large as 3 pF and a power consumption of about 3.5 mW. An extended tuning range can be achieved through the proposed linearization circuit that reduces the total harmonic distortion (THD) in the lower part of the tuning range. Simulation program with IC emphasis (SPICE) simulation results are presented, comparing the classical solution with respect to the linearized one; the input stage shows an output current THD less than 1% for an input differential signal of up to 500m V/sub pp/ over an almost 10:1 tuning range.<
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