A Novel Log‐Domain First‐Order Multifunction Filter

ABSTRACT A new log‐domain first‐order multifunction filter is proposed in this letter. The proposed filter is systematically derived using the state‐space synthesis procedure from a corresponding block diagram. It provides low‐pass (LP), high‐pass (HP), and all‐pass (AP) responses simultaneously for a single input signal. The filter circuit has a very simple structure since it uses only bipolar junction transistors (BJTs) and a grounded capacitor. It can be electronically tuned by changing an external current. The filter has a greater bandwidth due to its inherent current‐mode and log‐domain operations. PSPICE simulations are given to confirm the theoretical analysis.