Comparison of OpAmp Based and Comparator Based Switched Capacitor Filter

Abstract

Comparator based switched capacitor circuits provide an excellent opportunity to design sampled data systems where the virtual ground condition is detected rather than being continuously forced with negative feedback in Opamp based circuits. This work is an application of this concept to design a 1 st order 330 KHz cutoff frequency Lowpass filter operating at 10 MHz sampling frequency in 0.13µm technology and 1.2 V supply voltage. The Comparator Based Switched Capacitor (CBSC) filter is compared with conventional Two stage Miller compensated Operational amplifier based switched capacitor filter. It is shown that CBSC filter relaxes the constraints like speed ,linearity, gain, stability which would otherwise be hard to satisfy in scaled technologies in Opamp based circuits. The designed CBSC based lowpass filter provides significant power savings compared to traditional Opamp based switched capacitor filter.

A 1.8 V 64.9 uW 54.1 dB SNDR 1^st order sigma-delta modulator design using clocked comparator Based Switched Capacitor technique

“…The combination of a comparator and a current source realizes the same charge transfer as an OpAmp based implementation without the stability concern of high-gain and high-speed feedback loop. In conventional CBSC there is tradeoff between speed and accuracy [13]. Also conventional CBSC circuits consume a lot of power due to the continuous comparators present in CBSC circuits.…”