Design of a general biquadratic filter section with only transconductances and grounded capacitors

A method is presented for the implementation of all stable second-order filters using only tunable transconductance elements and grounded capacitors (TGC filters). Although other voltage-to-current converters can be used, the simple four-transistor transconductance is particularly convenient because of its reduced circuitry. The synthesis technique is based on the signal-flow-graph corresponding to the state-space model of a second-order section. The approach is general and can be applied to obtain higher-order filters in the same manner, provided that the corresponding signal flow graph exists.>