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Analysis of circuit conditions for optimum intermodulation and gain in bipolar cascomp amplifiers with non-ideal error correction

Analysis of circuit conditions for optimum intermodulation and gain in bipolar cascomp amplifiers with non-ideal error correction
Analysis of circuit conditions for optimum intermodulation and gain in bipolar cascomp amplifiers with non-ideal error correction
The cascoded-compensation or 'Cascomp' amplifier offers excellent distortion reduction and thermal distortion rejection, but has not seen widespread use because of a limited gain and increased complexity compared with other topologies. The original theory showed that with the addition of an ideal error amplifier the circuit will completely compensate distortion for suitably chosen degeneration and bias values. This research presents a new, rigorous mathematical proof for conditions of compensation. The authors further develop the proof to include the non-idealities of the error amplifier. It is shown that there exists a second bias point, not exposed by the original analysis that offers improved gain while maintaining distortion cancellation. By reducing the error amplifier degeneration resistance, one can increase a Cascomp circuit's overall gain by several dB while maintaining theoretically perfect distortion compensation. A robust bias point is proposed, which takes the advantage of this new theory by optimising circuit values resulting in a comparatively broader and deeper third-order distortion null. The proposed theory is confirmed with simulation and measurement that show agreement within the bounds of process and component error limits.
0956-3768
568-575
Balsom, T.
09714124-2869-4b5b-b6d0-eecbb459b629
Scott, J.B.
e284aabc-8109-49d1-a602-3700ba0c74f2
Redman-White, W.
d5376167-c925-460f-8e9c-13bffda8e0bf
Balsom, T.
09714124-2869-4b5b-b6d0-eecbb459b629
Scott, J.B.
e284aabc-8109-49d1-a602-3700ba0c74f2
Redman-White, W.
d5376167-c925-460f-8e9c-13bffda8e0bf

Balsom, T., Scott, J.B. and Redman-White, W. (2014) Analysis of circuit conditions for optimum intermodulation and gain in bipolar cascomp amplifiers with non-ideal error correction. IET Circuits Devices and Systems, 8 (6), 568-575. (doi:10.1049/iet-cds.2014.0105).

Record type: Article

Abstract

The cascoded-compensation or 'Cascomp' amplifier offers excellent distortion reduction and thermal distortion rejection, but has not seen widespread use because of a limited gain and increased complexity compared with other topologies. The original theory showed that with the addition of an ideal error amplifier the circuit will completely compensate distortion for suitably chosen degeneration and bias values. This research presents a new, rigorous mathematical proof for conditions of compensation. The authors further develop the proof to include the non-idealities of the error amplifier. It is shown that there exists a second bias point, not exposed by the original analysis that offers improved gain while maintaining distortion cancellation. By reducing the error amplifier degeneration resistance, one can increase a Cascomp circuit's overall gain by several dB while maintaining theoretically perfect distortion compensation. A robust bias point is proposed, which takes the advantage of this new theory by optimising circuit values resulting in a comparatively broader and deeper third-order distortion null. The proposed theory is confirmed with simulation and measurement that show agreement within the bounds of process and component error limits.

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More information

Accepted/In Press date: 23 June 2014
e-pub ahead of print date: 8 December 2014
Published date: 8 December 2014
Organisations: Electronics & Computer Science

Identifiers

Local EPrints ID: 378074
URI: https://eprints.soton.ac.uk/id/eprint/378074
ISSN: 0956-3768
PURE UUID: 6d837993-a3f4-4f50-80cc-2969a6ebc16e

Catalogue record

Date deposited: 26 Jun 2015 11:13
Last modified: 03 Aug 2018 16:35

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