No abstract

In this paper, an in-depth analysis of switched-resistor (S-R) techniques for implementing low-voltage low-distortion tunable active-RC filters is presented. The S-R techniques make use of switch(es) with duty-cycle-controlled clock(s) to achieve tunability of the effective resistance and, hence, the RC time constant. The characteristics of two S-R networks utilizing one set (S-1R) and two sets (S-2R) of switch and resistor combinations are analyzed. It will be shown that the S-2R network outperforms the S-1R counterpart in terms of finite-slew-rate-induced distortion, frequency translation, and noise performance. In order to extend the tuning range, an S-R bank scheme is also described. The theoretical analysis was verified by an experiment on a 100-kHz first-order S-R filter prototype, implemented using discrete elements, where several advantages of the S-2R over the S-1R networks are demonstrated. Simulations of 10-MHz low-pass filters based on the S-1R and S-2R techniques in a standard 0.18-m CMOS process are also included for performance comparison in practical on-chip filter implementations.

No abstract

OPAMP-RC integrators built with linear resistors and capacitors can achieve very high linearity. By means of a switched resistor, tuning of the RC time-constant is possible via VC the duty-cycle of the clock controlling the switched resistor. This R l paper analyzes the effect of OPAMP slew rate limitations on the Vjn°d istortion of a switched-resistor lossy OPAMP-RC integrator. We show via analysis and simulations that the use of two sets of AV switched resistors instead of one relaxes the OPAMP slew rate requirements, and reduces the resulting distortion significantly.

6 7 + 9 9 3 ) 1 / ) 0L )4;30;.8 L K nal flow graph of leapfrog filter and then realize each L promised. Unfortunately, several floating resistors are J /L J ) K the prototype RLC filters one by one. Current con-'KK3 K K J ) K J 6 L K J . L J /L K /99933 = J # Consider the general ladder structure in figure 1. Here RLC filter. The characteristic of this structure can be > J J J OGN L J