The University of Southampton
University of Southampton Institutional Repository

Digitally tunable continuous-time filters for VLSI

Digitally tunable continuous-time filters for VLSI
Digitally tunable continuous-time filters for VLSI

The development of a VLSI-compatible digitally tunable continuous-time filtering technique is described. Simple passive and active structures are combined in a standard op-amp RC configuration to realise very high signal performance. Each time-constant determining capacitor in the filter is replaced with a programmable array of highly linear passive capacitors. The array value is automatically fixed to correct process and temperature induced errors in the filters' RC time-constants. Linear polysilicon resistors and high performance single-ended or fully-balanced op-amps complete the design. A detailed description of the design of one such fully-balanced op-amp is given. The most suitable array and filter topologies are discussed with respect to performance, especially linearity. The code needed to fix the array values is derived using on-chipcalibration circuitry. A reference clock with fixed period is the only external requirement. A new calibration scheme is presented and its measured performance is discussed. The fabricated filters designed using the optimised techniques exhibit a mean dynamic range of + 95dB and a mean signal THD of around -90dB for a differential output signal of 2Vrms and a fundamental input signal frequency of up to 20 kHz. Such performance is compatible with the dynamic range of 16-bit sampled data processors. The area per pole of the most complex of these filters is comparable to that of other, lower performance, integrated continuous-time filters. A novel digitally tunable OTA-C filter is developed and shown (in simulation only) to have signal performance similar to that of the op-amp RC filters. A digitally tunable op-amp RC filter technique is extended and applied to the design of a fourth-order 1 bit Σ-Δ analogue-to-digital converter. The converter was fabricated and was fully functional with unconditional stability.

University of Southampton
Durham, Anna Mary
Durham, Anna Mary

Durham, Anna Mary (1992) Digitally tunable continuous-time filters for VLSI. University of Southampton, Doctoral Thesis.

Record type: Thesis (Doctoral)

Abstract

The development of a VLSI-compatible digitally tunable continuous-time filtering technique is described. Simple passive and active structures are combined in a standard op-amp RC configuration to realise very high signal performance. Each time-constant determining capacitor in the filter is replaced with a programmable array of highly linear passive capacitors. The array value is automatically fixed to correct process and temperature induced errors in the filters' RC time-constants. Linear polysilicon resistors and high performance single-ended or fully-balanced op-amps complete the design. A detailed description of the design of one such fully-balanced op-amp is given. The most suitable array and filter topologies are discussed with respect to performance, especially linearity. The code needed to fix the array values is derived using on-chipcalibration circuitry. A reference clock with fixed period is the only external requirement. A new calibration scheme is presented and its measured performance is discussed. The fabricated filters designed using the optimised techniques exhibit a mean dynamic range of + 95dB and a mean signal THD of around -90dB for a differential output signal of 2Vrms and a fundamental input signal frequency of up to 20 kHz. Such performance is compatible with the dynamic range of 16-bit sampled data processors. The area per pole of the most complex of these filters is comparable to that of other, lower performance, integrated continuous-time filters. A novel digitally tunable OTA-C filter is developed and shown (in simulation only) to have signal performance similar to that of the op-amp RC filters. A digitally tunable op-amp RC filter technique is extended and applied to the design of a fourth-order 1 bit Σ-Δ analogue-to-digital converter. The converter was fabricated and was fully functional with unconditional stability.

This record has no associated files available for download.

More information

Published date: 1992

Identifiers

Local EPrints ID: 461010
URI: http://eprints.soton.ac.uk/id/eprint/461010
PURE UUID: 12b8204c-dabb-4620-ac56-ed1215aab217

Catalogue record

Date deposited: 04 Jul 2022 18:33
Last modified: 04 Jul 2022 18:33

Export record

Contributors

Author: Anna Mary Durham

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of http://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×