A 2.7V elliptical all-MOS gm C-OTA filter

The gmC-OTA technique relaxes transconductor output swing and DC-gain requirements, which makes it a suitable candidate for low-voltage circuits. To reduce the power consumption of OTAs an excess-phase shift compensation with automatic tuning circuit is proposed. A floating triode region transconductor with a novel biasing to compensate the effect of channel length modulation is presented. The two independent common-mode levels in a gmC-OTA integrator are utilized to bias a PMOS as a linear capacitor. This enables the realization of the floating transmission zero capacitors with a pure digital CMOS process. The implementation and the experimental results for a 3rd order 2.7V all- MOS elliptical filter with 64dB dynamic range and 0.1% linearity are presented.