An ultralow-power CMOS transconductor design with wide input linear range for biomedical applications

This paper presents an ultralow-power CMOS linear transconductor design operating in weak inversion for low frequency g_m-C filter design for potential biomedical applications, where the transconductance should be low to reduce the capacitor size, and linear to minimize distortion. Bulk-driven and degeneration techniques are used, and we have adopted this G_m cell as a linear source degeneration resistor to achieve a 91% reduction in the transconductance value. In addition, a fourth-order Butterworth bandpass filter was designed in a proprietary 0.35-μm BCD (bipolar-CMOS-DMOS) process by Texas Instruments (TI). The SPICE simulation results indicate that the total harmonic distortion is greatly reduced to less than -71 dB at an input of 100 mV. The power consumption is only 750 nW at a 3-V supply voltage.