Design of a new log-domain differentiator based universal analog biquadratic filter
A novel implementation of a continuous-time universal analog biquadratic filter is presented. Using two log-domain differentiators along with a few current mirrors and current copiers, the low-pass, high-pass, band-pass, band-elimination (notch) and all-pass filter transfer functions are realized. The filter, has been designed using a purely current-mode approach and is electronically tunable over several decades of frequency by altering the magnitude of the current sources. Both the differentiators used here have been designed using bipolar junction transistors. The design can be extended and realized with MOSFETs operating in the weak inversion region. The concept has been demonstrated at circuit simulation level using the Saber simulator