Low-Voltage OTA-C Filter With an Area- and Power-Efficient OTA for Biosignal Sensor Applications.

This paper presents a systematic method for decreasing the amount of transconductors used by an operational transconductance amplifier-capacitor (OTA-C) filter to decrease the power consumption and the active area. An OTA with a local-feedback linearized technique and a transconductance booster is proposed based on the presented method. The proposed OTA combines current division with source degeneration to enhance linearity and implement low transconductance. This topology enables the proposed OTA to drive multiple integration capacitors without an additional output stage. The OTA-based circuit realizes low power consumption by operating under a weak inversion at a supply voltage of 1 V. Thus, a fifth-order ladder-type low-pass Butterworth OTA-C filter is implemented for the acquisition of electrocardiograph signals. The proposed method is validated using a prototype fabricated through a 1P6M 0.18-μm CMOS process. Results show that in ECG signal acquisition, the proposed filter has a signal bandwidth located within 250 Hz, a dynamic range of 61.2 dB, and a power consumption of 41 nW to achieve a figure-of-merit of 5.4 × 10-13. The active area of the filter is 0.24 mm2.