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Switched-capacitor filter design


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Alauddin, AM 1983 , 'Switched-capacitor filter design', Unspecified thesis, University of Tasmania.

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The switched-capacitor (SC) technique is a very attractive method for
implementing fully integrated filters in MOS technology.. The filters,
consisting only of switches, capacitors and operational amplifiers,
can be realised through a nutter of design procedures. This thesis
describes these design techniques and their applications.
Many of the suitable designs use SC integrators which can be easily
derived from the analogue active integrators. Parasitic-insensitive
implementation is possible realising either the lossless discrete
integrator (Lza) or the bilinear transformation. The effects of noise
and other non-idealities of the switches and operational amplifiers on
these integrators are described. A general biquadratic structure based
on the SC integrators is given from which a circuit capable of realising
bandpass transfer functions is derived. The SC biquads are cascaded or
coupled for the design of higher order filters. Higher order SC filters are also designed by simulating doublyterminated
'LC ladder networks with integrators using the LDI
transformation. Other methods of simulating the ladder network include
using voltage-controlled current sources, the impedance simulation
method and voltage inverter switches. These methods mostly produce
circuits which are sensitive to parasitic capacitances and are only
briefly described.
These design techniques are used to design SC filters which meet
the one-third octave bandpeds filter specification required for the
analysis of acoustic noiii and vibration. The midband frequencies of
the resulting SC bandpass filters can be varied from 10Hz to 20kHz.
The designs are made using clock frequency at a minimum value possible
and another at 48 times the midband frequency. The suitable circuits
are compared with regard to their requirements and performances.
The antialiasing problem due to the wide range of required midband
frequencies is overcome with the use of an SC decimator circuit. This
allows the antialiasing filter, the decimator and other accessories to
be implemented on 4 single Chip with the SC bandpass filter.
The SC circuits are analysed using their z-transform relations.
The nodal analysis technique and the equivalent circuit method are
described and used for deriving z-transform transfer functions of the
SC filters. These are then used to predict the frequency responses
of the filters and their sensitivity as to variation of one single
capacitor value.

Item Type: Thesis - Unspecified
Authors/Creators:Alauddin, AM
Keywords: Electric filters, Active
Copyright Holders: The Author
Copyright Information:

Copyright 1983 the Author - The University is continuing to endeavour to trace the copyright
owner(s) and in the meantime this item has been reproduced here in good faith. We
would be pleased to hear from the copyright owner(s).

Additional Information:

Thesis (M.Eng.Sc)--University of Tasmania, 1984. Bibliography: l. 175-180

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