First-order multifunction filter design using current amplifiers

This paper presents a new circuit realization capable of simultaneously realizing all three current-mode first-order filtering functions, namely the low-pass (LP), high-pass (HP), and all-pass (AP). The proposed circuit is created using three programmable current amplifiers (PCAs) and only two passive components, which includes one resistor and one capacitor. LP and HP filters have independently tuneable gain and pole frequency by means of “mu-factors”, while the AP filter has only tunable gains and the pole frequency is ideally controllable only by external passive components. The theoretical results are verified by SPICE simulations using transistor model process parameters NR100N (NPN) and PR100N (PNP) of bipolar arrays ALA400-CBIC-R from AT&T.