An electronically tunable multi-mode filter structure with feedback topology for the HF applications in multi-standard receivers

This work proposes a new 2nd order MOSFET-C filter circuit using only three MOSFETs in its core. The single-input multiple-output design provides current-mode (CM) and transresistance mode (TRM) low-pass (LP) and bandpass (BP) filters. A feedback loop using an OTA circuit enhances filter characteristics by improving the quality factor and increasing gain. This study is the first to apply feedback to a MOSFET-C-based filter for performance enhancement. The feedback circuit consists of six MOSFETs, adding only 200 µW power consumption without degrading performance. The circuit is electronically tunable, free from body effect, uses grounded capacitors, and operates at ± 0.9 V, making it suitable for low-voltage applications. Simulations were performed using TSMC 0.18 µm technology for both non-feedback and feedback structures. Monte Carlo analysis, THD responses, and input-referred noise equations were obtained. Post-layout simulations showed layout areas of 2887.2 µm² (non-feedback) and 6381.9 µm² (feedback). Experimental PCB implementations confirmed agreement with theoretical calculations and simulations. Thermal analysis showed no significant heat emissions. The results demonstrate that this architecture is well-suited for high-frequency (HF) applications in wireless receivers.