A CMOS linear tunable transconductor for continuous-time tunable Gm-C filters

A novel CMOS linear transconductor is presented. It is basically an improvement of the classical telescopic cascode OTA with source degeneration in which the resistor has been implemented using quasi-floating-gates transistors. It also allows compact implementation of common mode voltage control circuitry in order to save area and power consumption. This transconductor has been designed in a 0.5 mum CMOS technology and the results obtained show a THD of -61 dB at 10 Mhz for a 1 V_pp output voltage. In order to show the feasibility for the implementation of tunable Gm-C filters using the proposed transconductor, a 1 MHz tunable third order Chebyshev low-pass filter suitable for Bluetooth applications has been experimentally validated.