A Reconfigurable-Band Analog Filter Standard-Cell Based on Differential/Single Input Signaling

Abstract

This work presents a reconfigurable-band analog filter capable of performing the low-pass, high-pass, band-pass or all-pass functions. The proposed filter is a simple and compact cell composed of only two RC networks and one differential Operational Transconductance Amplifier (OTA). To select the desired filter type, two configurations must be done: 1) the two RC network shall be configured as low-pass/low-pass, high-pass/high-pass or low-pass/high-pass, 2) the input signals must be fed in differential or single mode. To validate theory and simulations, the proposed reconfigurable-band filter was designed, fabricated and measured to meet the biomedical band (0.1 Hz - 10 kHz) in a $0.5 ~\mu \text{m}$ CMOS standard fabrication process. To achieve the extremely low RC time constants imposed by the biomedical band, the R element was implemented using PMOS high-value programmable resistor. The prototype exhibits a silicon area of $470 ~\mu \text{m}$ x $250 ~\mu \text{m}$ and a power consumption of $96.32 ~\mu \text{W}$ using a ± 0.8 V symmetric power supply. Due to this circuit’s ability to perform four filter-functions, its operation band can be tuned over five decades, its power consumption is in the nano and micro-watt regime, and it is area compact, the proposed analog filter is a suitable candidate for being an analog standard-cell.

Keywords

• CMOS
• continuous-time filter
• analog standard cell
• universal filter
• very-low frequency