A general framework for performance optimization of continuous-time OTA-C
(Operational Transconductance Amplifier-Capacitor) filters is proposed. Efficient
procedures for evaluating nonlinear distortion and noise valid for any filter of arbitrary
order are developed based on the matrix description of a general OTA-C filter model .
Since these procedures use OTA macromodels, they can be used to obtain the results
significantly faster than transistor-level simulation. In the case of transient analysis, the
speed-up may be as much as three orders of magnitude without almost no loss of
accuracy. This makes it possible to carry out direct numerical optimization of OTA-C
filters with respect to important characteristics such as noise performance, THD, IM3,
DR or SNR. On the other hand, the general OTA-C filter model allows us to apply
matrix transforms that manipulate (rescale) filter element values and/or change topology
without changing its transfer function. The above features are a basis to build automated
optimization procedures for OTA-C filters. In particular, a systematic optimization
procedure using equivalence transformations is proposed. The research also proposes
suitable software implementations of the optimization process. The first part of the
research proposes a general performance optimization procedure and to verify the
process two application type examples are mentioned. An application example of the
proposed approach to optimal block sequencing and gain distribution of 8th order
cascade Butterworth filter (for two variants of OTA topologies) is given. Secondly the
modeling tool is used to select the best suitable topology for a 5th order Bessel Low Pass
Filter. Theoretical results are verified by comparing to transistor-level simulation withCADENCE. For the purpose of verification, the filters have also been fabricated in
standard 0.5mm CMOS process.
The second part of the research proposes a new linearization technique to
improve the linearity of an OTA using an Active Error Feedforward technique. Most
present day applications require very high linear circuits combined with low noise and
low power consumption. An OTA based biquad filter has also been fabricated in 0.35mm
CMOS process. The measurement results for the filter and the stand alone OTA have
been discussed. The research focuses on these issues.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/3925 |
| Date | 16 August 2006 |
| Creators | Ramachandran, Arun |
| Contributors | Sinencio, Edgar S |
| Publisher | Texas A&M University |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Thesis, text |
| Format | 1729833 bytes, electronic, application/pdf, born digital |
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