A Bootstrapped Analog Switch with Constant On-Resistance

Sang-hun KIM  Yong-Hwan LEE  Hoon-Ju CHUNG  Young-Chan JANG  

IEICE TRANSACTIONS on Electronics   Vol.E94-C   No.6   pp.1069-1071
Publication Date: 2011/06/01
Online ISSN: 1745-1353
DOI: 10.1587/transele.E94.C.1069
Print ISSN: 0916-8516
Type of Manuscript: BRIEF PAPER
bootstrapped analog switch,  input-sampling switch,  analog-to-digital converter,  on-resistance,  

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A bootstrapped analog switch with constant on-resistance is proposed for the successive approximation (SA) analog-to-digital converters (ADCs) that have many input-sampling switches. The initialization circuit, which is composed of a short pulse generator and a transmission gate, improves the linearity of the proposed bootstrapped analog switch by reducing the effect of the capacitive load. To evaluate the proposed bootstrapped analog switch, the 10-bit 1 MS/s CMOS SA ADC with a rail-to-rail differential input signal was designed by using a 0.18 µm CMOS process with 1.0 V supply voltage. The proposed bootstrapped analog switch reduced the maximum VGS variation of the conventional bootstrapped analog switch by 67%. It also enhanced the signal to noise-distortion ratio of the SA ADC by 4.8 dB when the capacitance of its gate node is 100 fF, and this improvement was maximized when the capacitance of its gate node increases.