BiCMOS current mode analog Nyquist filter at video rates

The authors present current-mode analog circuits used to implement a video-speed, phase-equalized low-pass filter. A cascade of biquads provide a uniform structure to meet both the magnitude and the linear phase requirements. The biquads use current conveyors configured as current-in, current-out integrators. The unity gain frequency of the integrators is determined by an RC product. A variable-gain current amplifier in series with the integrator can then change the unity gain frequency under electronic control. The resulting topologies are electrically programmable and exhibit low sensitivity to component variations. Simulation results of the Nyquist filter realized with these techniques are reported