title: Application of Nonlinear Transistor Characteristics

authors: Balsom, Toby

subjects: Transistor

abstract: This research presents three works all related by the subject of third-order distortion reduction in nonlinear circuits. Each one is a novel extension to previous work in that branch of electronics literature. All three follow the procedure of presenting a novel algebraic proof and following up with simulations and/or measurements to confirm the theoretical result. The works are generally themed around nonlinear low-frequency bipolar transistor circuits.
Firstly, an investigation is conducted into a well documented effect in bipolar-junction transistors (BJTs) called inherent third-order distortion nulling. This effect is shown to be a fundamental result of the transistor’s transfer junction acting upon an input signal. The proof of a single BJT emitter-follower amplifier’s inherent null is examined which is well documented in the literature. This forms the basis for a novel extension in Darlington transistors where theory suggests the third-order null occurs at double the collector current of a single BJT. Discrete measurements of a CA3083 transistor array are undertaken and compared with theory and simulation data. These measurements confirm theory with reasonable accuracy.
A temperature and process variation independent bias circuit is developed to solve one issue with using third-order distortion nulling. This work is interesting in that it branches into series resistance compensation for translinear circuits and stands as a useful circuit in its own right. Using stacks of matched forward-biased semiconductor junctions which conform to translinear conditions, a bias current can be generated which theoretically removes temperature and series resistance dependence on the particular BJT used. This proves useful for the previous work in distortion nulling, but also allows direct and accurate measurement of series resistance. Again, simulation and measurement data is obtained from discrete measurements of the proposed circuit, and the results conform with theory to a reasonable degree.
Lastly, this work presents the analysis of a cascoded-compensation (Cascomp) amplifier. It presents the first fully nonlinear derivation of the Cascomp’s transfer function and its associated harmonic and intermodulation distortion components. The derivation reveals an interesting characteristic in which the third-order intermodulation distortion has multiple local minima. This characteristic has not yet been presented in the literature, and allows better optimisation of Cascomp amplifiers in any application. Again, this characteristic and its potential benefits are confirmed with simulation and discrete measurements.
Observations of the presented works are discussed and built upon in the last chapter. This leads to suggestions on future research topics branching on from these works.

text: Application of Nonlinear Transistor Characteristics This research presents three works all related by the subject of third-order distortion reduction in nonlinear circuits. Each one is a novel extension to previous work in that branch of electronics literature. All three follow the procedure of presenting a novel algebraic proof and following up with simulations and/or measurements to confirm the theoretical result. The works are generally themed around nonlinear low-frequency bipolar transistor circuits.
Firstly, an investigation is conducted into a well documented effect in bipolar-junction transistors (BJTs) called inherent third-order distortion nulling. This effect is shown to be a fundamental result of the transistor’s transfer junction acting upon an input signal. The proof of a single BJT emitter-follower amplifier’s inherent null is examined which is well documented in the literature. This forms the basis for a novel extension in Darlington transistors where theory suggests the third-order null occurs at double the collector current of a single BJT. Discrete measurements of a CA3083 transistor array are undertaken and compared with theory and simulation data. These measurements confirm theory with reasonable accuracy.
A temperature and process variation independent bias circuit is developed to solve one issue with using third-order distortion nulling. This work is interesting in that it branches into series resistance compensation for translinear circuits and stands as a useful circuit in its own right. Using stacks of matched forward-biased semiconductor junctions which conform to translinear conditions, a bias current can be generated which theoretically removes temperature and series resistance dependence on the particular BJT used. This proves useful for the previous work in distortion nulling, but also allows direct and accurate measurement of series resistance. Again, simulation and measurement data is obtained from discrete measurements of the proposed circuit, and the results conform with theory to a reasonable degree.
Lastly, this work presents the analysis of a cascoded-compensation (Cascomp) amplifier. It presents the first fully nonlinear derivation of the Cascomp’s transfer function and its associated harmonic and intermodulation distortion components. The derivation reveals an interesting characteristic in which the third-order intermodulation distortion has multiple local minima. This characteristic has not yet been presented in the literature, and allows better optimisation of Cascomp amplifiers in any application. Again, this characteristic and its potential benefits are confirmed with simulation and discrete measurements.
Observations of the presented works are discussed and built upon in the last chapter. This leads to suggestions on future research topics branching on from these works.

year: 2014

title: Audience responses to news media images of Pacific health

authors: Loto, Robert

subjects: Maori

abstract: News media contain a multitude of images of Pacific peoples and health. This paper presents findings from a social psychological study of audience responses to such images. Two Pacific and two Palagi groups took part in discussions in which they responded to specific print media articles. These discussions were used to explore how different New Zealand audiences view and respond to the portrayals of Pacific people and their health. Responses from the Pacific and Palagi focus groups were compared showing both salience and difference in audience reactions. In appropriating aspects of news coverage, audience members do not simply regurgitate what they are shown by the media. They engage in complex dialogues with other audience members regarding issues raised by media coverage and in the process socially negotiate shared interpretations.

text: Audience responses to news media images of Pacific health News media contain a multitude of images of Pacific peoples and health. This paper presents findings from a social psychological study of audience responses to such images. Two Pacific and two Palagi groups took part in discussions in which they responded to specific print media articles. These discussions were used to explore how different New Zealand audiences view and respond to the portrayals of Pacific people and their health. Responses from the Pacific and Palagi focus groups were compared showing both salience and difference in audience reactions. In appropriating aspects of news coverage, audience members do not simply regurgitate what they are shown by the media. They engage in complex dialogues with other audience members regarding issues raised by media coverage and in the process socially negotiate shared interpretations.

year: 2008

title: Tū Māori Ake: Seeking which is above.

authors: Maxwell, Te Kahautu

abstract: Te Waka Āwhina 2015 Seeking that which is above Kaupapa - Philosophy o Aotearoa “Tū Māori ake” E ngā mana, e ngā reo, e ngā karangatanga, nei rā te powhiri ki a koutou katoa ‘MĀ TE MĀORI, MŌ TE MĀORI’ Te Waka Āwhina o Aotearoa National Training Hui by Māori for Māori within local government Āwhea: 2 – 4 February 2015 Ki whea: The Gallagher Academy of Performing Arts, The University of Waikato, Hamilton Hau kāinga: Te Puku o te Ika.

text: Tū Māori Ake: Seeking which is above. Te Waka Āwhina 2015 Seeking that which is above Kaupapa - Philosophy o Aotearoa “Tū Māori ake” E ngā mana, e ngā reo, e ngā karangatanga, nei rā te powhiri ki a koutou katoa ‘MĀ TE MĀORI, MŌ TE MĀORI’ Te Waka Āwhina o Aotearoa National Training Hui by Māori for Māori within local government Āwhea: 2 – 4 February 2015 Ki whea: The Gallagher Academy of Performing Arts, The University of Waikato, Hamilton Hau kāinga: Te Puku o te Ika.

year: 2015-02-03