UCM - Universal current-mode analogue structures

A novel current-mode analogue continuous-time filter synthesis technique is proposed based on a transformed set of state-equations, that allow the utilization of only current-mode linear lossy-integrators implemented using standard current mirrors; also a novel current-mode gyrator is introduced. The technique has been successfully used for synthesizing low-voltage 5th order lowpass, highpass, bandpass and stopband Chebyshev filters from passive doubly loaded ladder prototypes. SPECTRE simulations using CMOS standard process BSIM3 parameters have shown these filters perform well, exhibiting a THD less than 1% at 100 kHz for a 40 mV output (1 mu A input current) while the bias current per transistor is 10 mu A. Also, a Monte Carlo analysis has shown these filters preserve the low sensitivity inherent to the passive ladder prototype. The reduced number of small transistors necessary leads to small integration areas. The circuits have been fed with +/-1.5 mV power supplies.