A Wide Tuning Range Gm - C Continuous-Time Analog Filter

A Wide Tuning Range Gm-C Continuous-Time Analog Filter is a CMOS operation nal transconductance amplifier for low-power and wide tuning range filter application is proposed. The transconductor can work from the weak inversion region to the strong inversion region to maximize the transconductance tuning range. The trasconductance can be tuned by changing its bias current. A fifth-order Elliptic low-pass filter implemented with the transconductors is proposed to be implemented in SPICE using CMOS. The filter can operate with the cutoff frequency of 250Hz to 1MHz. The wide tuning range filter would be suitable for multi-mode applications, especially under the consideration of saving chip areas. The third-order inter-modulation of -40dB was measured over the tuning range with two tone input signals. The power consumption is 0.8mW at 1MHz cutoff frequency and 1.8-V supply. Cost and power consumption are two most important factors for these products. For the power consumption, digital circuits can benefit from the supply voltage reduction, but analog circuits can not necessarily decrease the power consumption with the decrease of supply voltage. To meet different specifications for low power consumption, new basic analog building blocks should be re-designed. Many of the previously published papers made efforts on improving the speed, linearity, or dynamic range of transconductor circuits. Key words—Analog CMOS design, OTA, Gm-C Filter, Weak-inversion region, Strong inversion region.