# Pseudo-N-path switched capacitor filters with out-of-band noise peaks

TL;DR: In this article, a pseudo-N-path (PNP) switched-capacitor (SC) integrator structure which avoids noise peaks in the main passband is described.

Abstract: Novel pseudo-N-path (PNP) switched-capacitor (SC) integrator structures which avoid noise peaks in the main passband are described. They combine the simplicity of the previously proposed RAM-type PNP SC circuits with the desirable properties of hybrid-type circuits. Simulation results are presented for filters employing these structures to verify their usefulness.

##### Citations

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10 May 1992TL;DR: System-level simulations showed that this modulator promises a 94-dB SNR as long as the DAC (digital-to-analog converter) linearity is at least 8 b, and so a gain-compensated version of one of them is presented.

Abstract: Simulation results on two switched-capacitor circuits suitable for use in a multi bit bandpass sigma-delta modulator are presented. The circuits use the N-path technique to guarantee accurate placement of the noise-transfer-function zeros. A 6th-order multibit bandpass analog-to-digital converter with a sampling frequency which is four times the center frequency and with a 5.5% bandwidth relative to the center frequency (the oversampling ratio equals 36) is described as a design example. System-level simulations, reported earlier, showed that this modulator promises a 94-dB SNR as long as the DAC (digital-to-analog converter) linearity is at least 8 b. The simulation results presented show that, in order to achieve this level of performance, the integrator circuits require high op-amp gain, and so a gain-compensated version of one of them is presented. The improved circuit requires an op-amp gain of 54 dB to achieve a modulator SNR of 90 dB. >

41 citations

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TL;DR: In this paper, a double-sampling pseudo-two-path bandpass /spl Delta/spl Sigma/ modulator is proposed, which has an output rate equal to twice the clock rate, uses n/2 operational amplifiers for an nth-older noise transfer function, and has reduced clock feedthrough in the signal path band.

Abstract: A double-sampling pseudo-two-path bandpass /spl Delta//spl Sigma/ modulator is proposed. This modulator has an output rate equal to twice the clock rate, uses n/2 operational amplifiers (op-amps) for an nth-older noise transfer function, and has reduced clock feedthrough in the signal path band. The required clocks can be simpler to implement than the conventional pseudo-two-path techniques. The measured signal-to-noise ratio and dynamic range of the fourth-order double-sampling pseudo-two-path bandpass /spl Delta//spl Sigma/ modulator in a 30-kHz bandwidth at a center frequency of 2.5 MHz (at a clock frequency of 5 MHz) are 62 and 68 dB, respectively.

30 citations

### Cites background from "Pseudo-N-path switched capacitor fi..."

...Since there is a noise peak in the center of the passband, several improved versions were presented [8]–[10]....

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03 May 1993TL;DR: The present state of the art of switched capacitor (SC) circuits is reviewed, and the most commonly used stages are described, and some circuit techniques developed over the past few years are reviewed.

Abstract: The present state of the art of switched capacitor (SC) circuits is reviewed. Typical applications are listed for micropower as well as other systems. The most commonly used stages are described, and some circuit techniques developed over the past few years are reviewed. The intrinsic limitations of SC techniques are listed and compared with those of more recently introduced switched current (SI)-based circuits. >

13 citations

01 Jan 2002

TL;DR: In this paper, Temes et al. proposed a low-voltage switch-capacitor circuit for low-power bandpass analog-to-digital (L2D) converters.

Abstract: approved: abor C. Temes and Un-Ku Moon The most accurate method for performing analog signal processing in MOS (metal-oxide-semiconductor) integrated circuits is through the use of switchedcapacitor circuits. A switched-capacitor circuit operates as a discrete-time signal processor. These circuits have been used in a variety of applications, such as filters, gain stages, voltage-controlled oscillators, and modulators. A switched-capacitor circuit contains operational amplifiers (opamps), capaciuors, switches, and a clock generator. Capacitors are used to define the state variables of a system. They store charges for a defined time interval, and determine the state variables as voltage differences. Switches are used to direct the flow of charges and to enable the charging and discharging of capacitors. Nonoverlapping clock signals control the switches and allow charge transfer between the capacitors. Opamps are used in order to perform high-accuracy charge transfer from one capacitor to another. The goal of this research is to design and explore future low-voltage switchedcapacitor circuits, which are crucial for portable devices. Low-voltage operation is needed for two reasons: making reliable and accurate systems compatible with the submicron CMOS technology and reducing power consumption of the digital circuits. Redacted for Privacy To this end, three different switched-capacitor integrators are proposed, which function with very low supply voltages. One of these configurations is used to design a lowpass L modulator for digital-audio applications. This modulator is fabricated and tested demonstrating 80 dB dynamic range with a 1-V supply voltage. The second part of this research is to show that these low-voltage circuits are suitable for modern wireless communication applications, where the clock and signal frequencies are very high. This part of the research has focused on bandpass analog-to-digital converters. Bandpass analog-to-digital converters are among the key components in wireless communication systems. They are used to digitize the received analog signal at an intermediate center frequency. Such converters are used for digital FM or AM radio applications and for portable communication devices, such as cellular phones. The main block, in these converters, is the resonator, which is tuned to a particular center frequency. A resonator must be designed such that it has a sharp peak at a specific center frequency. However, because of circuit imperfections, the resonant peak gain and/or the center frequency are degraded in existing architectures. Two novel switched-capacitor resonators were invented during the second part of this research. These resonators demonstrate superior performance as compared to previous architectures. A fourth-order low-voltage bandpass /I modulator, using one of these resonators, has been designed. © Copyright by Mustafa Keskin December 7, 2001 All Rights Reserved Low Voltage Switched Capacitor Circuits for Lowpass and Bandpass i Converters

5 citations

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14 Mar 1997

TL;DR: approved: Abstract approved: Prof. Gabor C. Temes

Abstract: approved: Abstract approved: Prof. Gabor C. Temesapproved: Prof. Gabor C. Temes

3 citations

### Cites background from "Pseudo-N-path switched capacitor fi..."

...The proposed differential and singleended novel PNP integrators address this problem [76]....

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...Conclusions In this chapter it has been shown that the proposed [76] PNP integrators are very attractive with their simplicity, immunity to the clock feedthrough noise, and speed improvements....

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##### References

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01 Jan 1986

TL;DR: In this article, the authors present an overview of the non-ideal effects in Switched-Capacitor Circuits, as well as their application in switch-capacitor circuits.

Abstract: Transformation Methods. MOS Devices as Circuit Elements. MOS Operational Amplifiers. Switched-Capacitor Filters. Nonfiltering Applications of Switched-Capacitor Circuits. Nonideal Effects in Switched-Capacitor Circuits. Systems Considerations and Applications. Index.

923 citations