Circuit for time constant tuning of gm-C filters
 This invention is an electronic time constant tuning circuit that uses a frequency of a clock to tune the circuit time constant. A first transconductor is used to charge a capacitor to two different voltages, each for a separate portion of a clock period. A second transconductor is used to compare the two voltages and control them to be equal by controlling the transconductance of the first transconductor. When the two voltage are equal, the resulting transconductance and the capacitance of the capacitor form the circuit time constant. The circuit time constant can readily be changed by changing the frequency of the clock. The control signal generated by the second transconductor can be applied to other transconductors in a gm-C filter to adjust the cutoff frequency of the filter when the other transconductors have a similar structure to the first transconductor. 
Tritech Microelectronics, Ltd.
H
H03H
inventional
Lijun
Luo