A MOSFET-C variable equalizer circuit with simple on-chip automatic tuning

The authors report a MOSFET-C variable bump equalizer architecture in MOS technology. The architecture is CAD-compatible in that it has a fixed physical layout, yet it achieves independent and continuous programmability of the three equalizer parameters ω₀ (center frequency), BW (bandwidth), and G (gain), using DC control voltages. To compensate for process and temperature variations the equalizer is tuned using a novel and simple master-slave automatic tuning scheme based on a switched-capacitor resistor in a gain control loop. The nonideal effects of the equalizer circuit due to finite amplifier gain bandwidth are studied, and a test chip is fabricated using the MOSIS 2-μm p-well double-poly CMOS process to verify the performance. The equalizer with the automatic tuning circuit occupies 1.25 mm² and operates from ±5-V power supplies. It dissipates 60 mW and provides wide tuning ranges for ω₀, BW, and G with less than 2.8% change in ω₀ over a 40°C temperature range