Pure-mode G(m)-C biquad filters

A continuous time differential voltage mode G(m) - C biquad and its adjoint current-mode version are described, employing FCS (floating current source ) circuits as building blocks. The biquad operates in the pure mode, i.e. n o resistors are used to convert internally voltage into current or vice ver sa. Both f(p) and Q(p) are tunable by current sources applied externally. T he current mode version is capable of providing values of Q(p) similar or e qual to 160. Due to the increasing Loop transmission, THD improves signific antly towards low frequencies. The input stage of the voltage mode version employs two OTAs, whose outputs are connected in parallel in order to add t heir differential inputs. This results in the hitherto unnoticed property o f subtracting their common mode input, providing an open loop gain which is high for differential, but low for common mode signals.