Design of low-noise switched-capacitor low-pass filters with adaptive configuration

Noise and area consumption has been a tradeoff in circuit design. Especially for switched-capacitor filters (SCF), kT/C noise gives a limitation to the minimum value of unit capacitance. In case of SCFs with a large capacitance spread, this limitation will result in a large area consumption due to large capacitors. Charge scaling technique combined with correlated double sampling gives a solution to this problem [18]. However, due to a fixed topology, the conventional designs suffer from lower signal-to-noise ratio (SNR) with small input voltages. When capacitance reduction is less crucial, there is a room to improve the SNR. This paper proposes an SCF with adaptive configuration to improve the SNR at small input signals. The proposed technique can reduce the output noise voltage by 30% for small input signals.