Title :
SC-filter structures with reduced requirements on op-amp bandwidth and settling time
Author :
Löfmark, Bengt G.
Author_Institution :
Ericsson Telecom AB, Stockholm, Sweden
Abstract :
Switched-capacitor (SC) filters designed from the state-variable equations of LC-filters with coupled-coil Brune sections have no time-continuous loops, and thus no positive feedback loops except through switched-capacitors. This leads to a reduced requirement on op-amp speed. By imposing certain restrictions on the coupled-coils inductance ratio, it is also possible to remove the summing capacitors, when the coupled-coil is embedded between single elements, which will further improve the sensitivity to the gain-bandwidth product. A fifth-order lowpass filter is taken as an example, showing the increased performance with this structure
Keywords :
active filters; band-pass filters; low-pass filters; network analysis; operational amplifiers; switched capacitor filters; LC-filters; SC-filter structures; continuous-time active filters; coupled-coil Brune sections; coupled-coils inductance ratio; fifth-order lowpass filter; op-amp bandwidth; settling time; state-variable equations; switched-capacitors; Band pass filters; Bandwidth; Capacitors; Coils; Couplings; Equations; Feedback loop; High power amplifiers; Operational amplifiers; Performance gain;
Conference_Titel :
Circuits and Systems, 1988., IEEE International Symposium on
Conference_Location :
Espoo
DOI :
10.1109/ISCAS.1988.15208
