Tunable Ccii-mosfet-c Filter Biquads for Video Frequencies

This paper describes two related topics. First, it is shown how the concept of the MOSFET-C integrator can be extended to single-amplifier filter biquads. Then a new differential-input balanced-output current conveyor (CCII) is presented, which has two essentially symmetrical and balanced signal paths. Using this CCII, a 4th-order lowpass filter cascade suitable for on-chip tuning is presented, whose passband edge frequency is tunable from 2 MHz to 4.5 MHz and whose pole Qs are fine-tunable to within 5%. Our simulation shows that the filter’s total harmonic distortion is below 1% and that the filter dissipates only 2 mW per pole pair at 3V supply voltage. Finally it is shown how bandpass and highpass filters can be built using the same technique.