Comments on "CMOS differential difference current conveyors and their applications"

For original paper see ibid., vol. 143, no. 2, p. 91-96 (1996 ). Recently Chiu, Liu, Ivan and Chen introduced a new active building block called a differential difference current conveyor (DDCC) and demonstrated its application in realising squarer, square rooter and multiplier circuits, differential integrators, and voltage mode (VM) and current mode (CM) low-pass/band-pass (LP/BP) filters. CMOS integrable implementations for DDCC⁺ and DDCC^- (two separate circuits) were also proposed. This comment extends the domain of application of the DDCC to the realisation of CM all grounded passive elements (AGPE) SRCOs, not discussed by Chiu et al. or anyone else so far. In particular, we show that, if instead of considering DDCC⁺ and DDCC^- as separate units, we consider a single unit which we call a differential difference complementary current conveyor (DDCCC), then such a DDCCC turns out to be a versatile device to implement CM AGPE SRCOs