Design of a low-distortion bootstrapped switch for non-uniform sampling of biomedical signals

The variations of the biomedical input signals at low frequencies, change the transistor’s threshold voltage in the conventional CMOS switch circuits which causes an increase in the distortion performance of the sampled signal. This paper proposes a new differential bootstrapped switch structure which can be employed at low frequencies for non-uniform sampling of biomedical signals. The proposed circuit structure includes the modified NMOS and PMOS bootstrapped switches to effectievely reduce the total harmonic distortion (THD). The On-Resistance (R_on) of the proposed bootstrapped switch at low frequencies is obtained as of less than 300 Ω. The post-layout simulations of the proposed circuit verify the good low-distortion performance of the proposed circuit, that can be employed properly at bio-signal processing applications of up to 1 kHz, at 1.8 V supply voltage in 0.18µm CMOS technology.