Electronically-Tunable Current-Mode Biquad Design Using MO-OTAs

In this paper, electronically-tunable, current-mode biquad is proposed by using multiple-output operational transconductance amplifiers (MO-OTAs). The proposed circuit has one input and two outputs. Without changing the circuit topology, low-pass (LP), and band-pass (BP) responses can be realized. The filter is realized by using two MO-OTAs, a single-output OTA (SO-OTA), a two-output OTA and two grounded capacitors. The biquad is designed based on first-order LP filter or lossy integrator blocks. The feedback block is applied to the filter circuit in order to obtain high quality factor values greater than 1/2. The center frequency and the quality factor of the LP and BP filters can be electronically tuned by DC current of OTAs. The total power dissipation of the proposed biquad is approximately 10mW at +/- 3V supplied voltage. The theoretical analysis is also confirmed with SPICE simulations.