A CMOS transconductor for multi-mode mobile channel selection filter is presented. The transconductor includes a voltage-to-current converter and a current multiplier. Voltage-to-current conversion employs linear region MOS transistors and the circuit features high linearity over a wide input swing range. The current multiplier which operates in the weak inversion region provides a wide transconductance tuning range without degrading the linearity. A third-order Butterworth low-pass filter implemented with the transconductors was designed by TSMC 0.18-μm CMOS process. The measurement results show that the filter can operate with the cutoff frequency of 135 kHz to 2.2 MHz. The tuning range and the linearity performance would be suitable for the wireless specifications of GSM, Bluetooth cdma2000, and Wideband CDMA. In the design, the maximum power consumption at the highest cutoff frequency is 2 mW under a 1-V supply voltage.