A novel CMOS linear transconductance cell for continuous-time filters

A novel tunable transconductance cell with extended linearity is described. It is based on the use of the transconductance of an MOS transistor operated in the triode region. High linearity of the cell is achieved by maintaining both drain-to-source and source-to-body voltages of the transistor constant by means of a very simple feedback loop. The tuning of the transconductance cell is obtained by adjusting the current delivered by a current source. The cell also provides high operation speed. The circuit is suitable for the design of high-performance, high-frequency, continuous-time filters. It is shown that, when the cell is used in a fully differential configuration, harmonic distortion as low as 0.3% can be achieved for processed signals with a peak amplitude of 3 V.<>