A 20 MHz fully-balanced transconductance-C filter in 2 μm CMOS technology

The design of a third-order elliptic low-pass LC ladder filter based on operational transconductance amplifiers (OTAs) which have good linearity over a large input range is presented. The design considerations are focused on high-frequency response, large signal-to-noise ratio, and notch depth, parameters which are all affected by parasitics. The filter is laid out with careful placement and routing to reduce parasitics, and is fabricated in 2-μm CMOS technology through MOSIS. The measured results show that the cutoff frequency of the filter is 20 MHz, the signal-to-noise ratio is 70 dB, the notch depth is 60 dB, and the total harmonic distortion is less than 1% over a 2-V peak-to-peak input range