Distortion analysis of bootstrap switch using Volterra series

Abstract

Linear behaviour of bootstrap switches is of critical importance in low-voltage analogue circuits and understanding the major factors affecting the linearity helps design a better switch. This study presents a theoretical approach for evaluating the distortion of bootstrap switches in the frequency domain based on the Volterra series. Five major factors affecting the linearity of the bootstrap switch are examined. In order to obtain a general design guideline the analysis is done in two parts. First, the distortion because of the nonlinear I-V characteristic of the main transistor of the switch is considered. In the second part, the distortion because of sampling errors, such as clock feed-through and charge injection, are added to the analysis. The theoretical results are verified by circuit simulations in a 0.18 mm CMOS process, using HSpice. 2 Volterra series and harmonic distortion The non-linearity of a system can be obtained using the Volterra series. A non-linear system with input x(t) and output y(t) can be represented by Volterra series as the sum of infinite number of operators as the following [5] y(t) ¼ H 1 [x(t)] þ H 2 [x(t)] þ H 3 [x(t)] þ Á Á Á (1) where H n [x(t)] is the nth-order operator with kernel h n and is

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