CFOA-based simple mixed-mode first-order universal filter configurations

This brief communication presents two current feedback op-amp (CFOA)-based simple first-order mixed-mode universal filter topologies-one of them providing first-order low-pass (LP), high pass (HP), and all pass (AP)-all the three filters in voltage-mode (VM)/trans-admittance-mode (TAM) while the other one realizing the quoted three functions in current-mode (CM)/trans-impedance-mode (TIM). Except the all pass filter realization from the first configuration which needs a second CFOA also as gain-of-two amplifier, in all the remaining cases of both the configurations, only a single CFOA is needed. The other notable features of the circuits are employment of only three resistors and a grounded capacitor (as preferred for IC implementation) and the availability of independent tunability of the gain (H-0) and cut-off frequency/pole frequency (omega(0)) of all the three filters, in both the cases. In spite of not offering ideally infinite input impedance in VM/TAM mode and ideally zero input impedance in CM/TIM mode, the circuits still possess easy cascadability due to providing a voltage output from a low-output impedance terminal W while the current output from the high output impedance terminal Z. Non-ideal and sensitivity analyses have also been carried out. The workability of the proposed circuits has been demonstrated through PSPICE simulations and experimental results using the commercially available AD844-type IC CFOA.