High-frequency Voltage-controlled Continuous-time Lowpass Filter Using Linearised Cmos Integrators

The design and implementation of a continuous-time lowpass filter with voltage-controlled cutoff frequency and passband ripple is presented. The circuit uses a linearised CMOS transconductor as a basic integrating building block. A voltage-controlled phase-adjusting scheme is employed in the integrator to compensate for excess phase in the transconductance at high frequencies. The fabricated filter is capable of realising cutoff frequencies as high as 2 MHz and handles single-ended input signals up to 4 V p-p with less than 1% distortion.