New universal voltage-mode LT1228-based second-order filter with SIFO-type and TISO-type configurations

This paper presents a new voltage-mode (VM) second-order universal filter (SUF) based on three available LT1228 commercial integrated circuits (ICs), featuring three high-input and low-output (HILO) impedances and offering either a single-input-five-output (SIFO) configuration or a three-input–single-output (TISO) configuration. The proposed VM SUF circuit comprises three LT1228s, two grounded capacitors, and six resistors. A notable feature of this design is its ability to operate in both SIFO and TISO configurations using a single circuit topology. In the SIFO-type filter, the VM SUF can simultaneously provide low-pass (LP), high-pass (HP), band-pass (BP), regular notch (RN), and all-pass (AP) filter responses. In the TISO-type filter, all five responses can be obtained by selecting appropriate input voltages. Additionally, the circuit can achieve two other low-pass notch (LPN) and high-pass notch (HPN) responses under specific conditions. The ability to synthesize all standard filtering functions in SIFO and TISO configurations from the same topology. PSPICE simulations and experimental results using three LT1228 commercial ICs demonstrate the feasibility of the proposed VM LT1228-based SUF configuration.